This style of advertising called "incentivized co-registration" (co-reg / co-reg path) (1) has been a long running plague - as far back as 2008 the FTC penalized ValueClick ~$3m (2) for this exact same thing as it's deceptive.
On the front-end you've got Facebook, Microsoft, and Google (to name a few) making money hand over fist letting these co-reg paths buy their media.
(As an aside Bing is well known to be the loosest with regulating compliant advertising which is just sad given that it impacts the MSFT brand.)
On the back-end you've got brands like Netflix, Nokia, Guiness, GAP, etc etc that lend themselves to being on the co-registration path and offering a variety of offers like "Join our newsletter etc" so they can then market to the consumers that say yes.
Again, great in concept - fill out your information once to enter for a "prize" and then select brand offers that you're interested in.
The problem is that most of the guys running the actual paths - buying the media etc - are small affiliate marketers. These are one to five man teams that slap together a variety of these co-reg offers from the "legit" co-reg company APIs.
So you'll see the big co-reg companies bragging about how they power the USAToday.com registration process, but the reality is many of them make the bulk of their revenue through their API sets and affiliate programs, which they leave damn-near unregulated (unless put under the microscope).
So every now and again the FTC hammers a few of these small timers, but the reality is an affiliate - doing "ok" - can make anywhere from $10 - 100k/mo in profit just doing what I describe above - build some direct-response landing pages, pull brand offers from the co-reg company apis, and buy media from companies that love to sell it, and don't look too hard for reasons not to.
So anywho I love getting on my soapbox but it's insane how many huge companies benefit from these scams, and how simple it is for them to have deniability due to the ecosystem of using these small timers on the front end.
(1) A great breakdown of "what is" co-reg advertising http://www.coregmedia.com/demos/demo-pub.php
(2) FTC Settles w/ValueClick http://www.ftc.gov/opa/2008/03/vc.shtm