This is something that doesn't often cross internet users' minds. Why would we need an alter ego for the use of the Net? It makes more sense the last decade, as scams, identity theft and spam have exploded into full blossom. You should not use your regular email address for these "potentially harmful" submissions.
You may very well be the win a free PS3 by signing up for some 'click here' popup advertisement. Chances are you won't, but if you want to try- use a new "trash account email" that won't lead your regular email address to spammer lists. Generally this is what these ads are supposed to accomplish. You enter your email address and so do a number of other people. Then, a mailing list is compiled and sold to email marketers. The same can be said for coupon sites and "members only deal sites.
A new email address like firstname.lastname@example.org or email@example.com won't solve your problem, but you are going to be visiting that mailbox looking for an email from your son, employer, or bank. It is merely a way to register and not worry about your real email's security. Remember this when you are in the stores this holiday season signing up for credit cards or special offers too.