One type of spam that shows up occasionally is spam that advertises your chance to get the hot technology item of the day - currently, that's typically an iPad or an iPhone - for "free". Here's a typical example:

Subject: We are looking for iPad testers We are looking for people who will be willing to test the iPad. The testing period will take 60 days. You only need to review and looking for bugs. After test you get to keep your iPad. You have no obligations. Spots are closing fast, so hurry and confirm your email address.

Sounds good, right?

If you go to the advertised site, you'll find a large picture of an iPad, with a list of mouth-watering specs and the words 'Testers Wanted', plus a field to enter your email address. All you have to do is type in your address and that iPad could be yours.

Not so fast. If you look a little lower on the page, you'll find a lot of small print. There isn't actually anything about testing. It turns out that to get your 'free' iPad, you have to 'complete the rewards bonus survey' and 'complete a total of 13 sponsor offers'.

The first problem is the survey. After you've filled it out, the company running the scheme has a lot of information about you that they can sell on. There's going to be a lot of junk mail in your future, and you can't even give them a false address because otherwise you'll never get your free iPad. But even if you don't mind that, the real problem is those 'sponsor offers'.

To get your free iPad, you have to sign up for a certain number of these 'offers'. Many of them are introductory offers: you get to try a service for a certain number of months, after which you can cancel your subscription. Some of them are of the kind where you buy something — books, DVDs — at an initial low price, and then agree to buy a fixed number at a higher price over the next year. Others might require you to apply for a credit card. The common theme is that you sign up for something and then you get regular bills until you cancel your subscription or until the term of the agreement ends. The sponsor, of course, will do everything they can to ensure that you don't cancel your subscription. In the shadier cases that involves customer support email addresses that never respond and telephone support lines that leave you on hold forever.

Companies offering these deals run from nationally-known names like Netflix or the New York Times, to some of the same companies that feature regularly in affiliate spam - Gevalia, 4SeasonsWineClub, Orchard Bank, Seattle Coffee Direct - to other companies with, frankly, questionable reputations. The signup site displays a list of 'representative' offers, but you don't get to see what's actually on offer and what the actual terms are until you sign up.

Let's back up and think about how this works for a moment. The company offering the 'free' iPad (remember that free iPad? Not looking quite so 'free' now, is it?) makes its money by driving you to these advertisers. They can make their money in one of three ways.

One, they can simply cheat you: when you've jumped through all the hoops and you ask for your free iPad, they can invent a reason why you don't qualify or they can simply ignore you. In a few weeks, their website goes away and a few weeks after that they're back again, doing business under a new name. If this happens to you, it's no use complaining to Netflix or the New York Times. They weren't the ones who promised you a free iPad.

There have been enough reports to suggest that many 'sponsor offers' operators are simply scammers. The companies are essentially anonymous: just a domain name and an address that may or may not be real. If they cheat you, good luck trying to track them down.

A second trick is to make it impossible for you to qualify. They can structure the offers in such a way that you can't or won't complete the requisite number or, if you do, the cost is ridiculously high. This structuring of offers is, in fact, key to many of these schemes. The first few offers might seem reasonable enough, but by the time you get to number thirteen, the choice has narrowed dramatically and you find yourself being required to pay large amounts for something you don't want. This technique rests on a psychological fact that is also exploited by 419 scammers: the more money you've sunk into something, the less likely you are to back out. So just as a 419 scammer will start by asking for small amounts of money, sponsor offers schemes begin by luring you in with inexpensive, attractive deals like a trial Netflix subscription. It's when you've met most of the requirements that they bring out the offers you don't want or can't afford. If you back out now, you can kiss goodbye to your 'free' iPad and they pocket the money. If you don't back out, you're on the hook for whatever they want to sell you. The psychology says that you won't back out. Either way, they win.

But let's suppose they're absolutely honest. You complete the offers and they send you a free iPad. How do they make their money?

They make their money by getting a commission from the sponsors whose offers you accept. Let's be totally unrealistic and say that each of the sponsors shares 50% of the money that you spend with them with the people giving away the iPad. That 64GB iPad they're showing on their website currently costs $700. Call it $775 after tax and shipping. For them to even break even on the deal, you have to spend $1550 with their sponsors. And that's without covering their running costs and profit. Let's say $1600 minimum.

But that 50% share is absurdly high. It's likely that their cut is actually closer to 5-15%. So they really need you to spend anywhere from $5,500 to $16,500 to get that 'free' iPad. You've also given away your personal information (remember that survey?) and you've signed up for some subscriptions that are going to be really hard to cancel. Congratulations: you just got screwed. Enjoy your iPad.

One last question: who's sending that spam? The signup website for the sponsor offer scheme is actually better-gifts.net, but that's not the domain that appears in the spam messages. That might be called something like i4tests.com. If you look at i4tests.com you'll see that it's just loading the better-gifts.net page in a frame. It's also sending a string of numbers that is probably an affiliate URL.

So the spammer — whose domain is hosted in Romania — is probably just an affiliate of better-gifts.net (remember to add their referral fee into your calculations when figuring how much better-gifts.net needs to make to break even). better-gifts.net would no doubt be shocked, just shocked to learn that their affiliate is sending spam. The spammer, of course, is free to claim anything they want to get you to go to the site: remember how they claimed that 'you only need to review and looking for bugs' ? The actual better-gifts.net site doesn't actually say anything about that. It does say 'Testers Wanted: Free', with the word 'free' placed in such a way that you can't really tell if they're promising you a free iPad or saying that they want free testers, but the small print makes it clear that this has nothing to do with testing and everything to do with signing up for sponsor offers.

better-gifts.net is probably also an affiliate, either of the sponsors or of whichever syndicated marketing company is administering the schemes for them. So if better-gifts.net turns out not to be honest and you don't get your iPad, it isn't the fault of Gevalia or 4SeasonsWine. better-gifts.net isn't responsible for the spam or for whatever lies the spammer writes. The sponsors aren't responsible if better-gifts.net cheats you. It's plausible deniability all the way down.

Everyone in the chain — the spammer, the sponsor offer site, the sponsors — profits. One person loses - the sucker who just tried to buy a 'free' iPad for ten times the regular price.

Oh, and as Steve Jobs, father of the iPad, likes to say, there's one more thing. That domain better-gifts.net? I don't know if they're honest or not, but the identity of the owner is hidden by a private registration at a registrar in China. Feel free to draw your own conclusions from that.