Registering for forums and other sites is something that is required at most of em by now. It’s a pitty because sometimes you just want to check something, or download something from one of those sites without having to go through yet another registration form, because you simply don’t intend to spend a lot of time there in the first place.
Besides, spreading your e-mail address all over the place is just a certain way to get more spam, so that’s just one more reason not to get it into another database.
While a lot of times I just refuse to register, there might be a solution to use the sites features anyway, and stay somewhat anonymous.
Check out BugMeNot, a site that provides a way to “share” user accounts for registration requiring sites. Currently they are up to 19.606 sites, which ain’t bad, but if one ain’t in there yet, you’re free to add it yourself.
There’s even a Firefox extention for it, which makes checking for a usable account so much easier.
With Mailinator you can “create” any e-mail address on the fly, and check it later on to see if anything arived.
Spammotel works as a forwarder where you can create an unlimited (well, probably not, but I bet its plenty) number of randomly generated e-mail addresses linked to your real address. If spam starts arriving from a certain site, you’ll be able to identify it uniquely, and block it if wanted.