One word: Spam You can't rely on things like captcha's, not anymore. But requiring an email address is at least a small difficulty. And if you get a whole bunc

One word: Spam You can't rely on things like captcha's, not anymore. But requiring an email address is at least a small difficulty. And if you get a whole bunch of signups from a single domain in a short period (And it's not, say, gmail) you know something's up.