Reminded by this article at Neowin
http://www.neowin.net/news/ebook-publishers-are-spying-on-us
I just wanted to say how I handle some of this stuff... When it might be useful I set up more-or-less throw-away accounts that won't necessarily lead anyone back to me. How far I go depends on how much I don't want to be tracked. With the Game Fly game giveaway I just used a credit card I got from a rebate -- there was no cost involved, their password limits made it a bit less secure, & as general practice I try to have our bank info stored on as few sites/servers as possible. I've got a separate Amazon acct. for Kindle books I download to my tablet -- I can't easily enter the same complicated password we use for our main acct., & if someone gets into the tablet & then into that acct. it won't do them too much good. If I was inclined to download some of **Those** books, magazines, &/or videos I'd have a 3rd acct., probably with fake info for obvious reasons... even inferred demographic data has a way of getting around. Another thing I'll use from time to time is the TOR Browser, a portable version of Firefox that uses, goes through the TOR network to hide my ip address -- not all forums or sites are as nice as this one, & there's a [mostly minor] bit of mischief that can be done using your ip that I'd rather not bother with.
I'm especially careful of this sort of thing here in the U.S. now that we're in a particularly nasty election season -- http://en.wikipedia.org/wiki/Swatting talks about a rather extreme way [someone could easily get killed] partisan minded folks can get carried away trying to get even with the other side. Some stores &/or sites can be targeted because they're seen as partisan, correctly or not, & *Any* user data, however it's gotten, used in the worst ways.