I've been wanting to do this since the days of IH_Code_Monkey_Gary. We need to add something to the user registration process.
1. E-mail checking - it checks if you are signing up but already have an account. 2. E-mail verification - send out an e-mail with a random number and asks you to click it. 3. A verified e-mails gets you to 3 posts/day. 4. A new account has 0 posts/day until e-mail verification is complete.
This will cut down on the invalid accounts and multiple aliases.
I want to go a step further. If someone signs up AGAIN with the same e-mail, don't tell them it's invalid, send them to the registration screen and fake it. Let them spend all day trying to figure out what is broke. <g>