So, why don't we use captcha, or have a waiting period for registration?

Maybe things have changed for registration, but it certainly doesn’t seem so, I’ve been away from the collective for a while but currently there is a crapload of spam questions, and plenty of old questions which have had spam responses in my alerts.

Why don’t we upgrade the registration system to counteract this? Maybe with recaptcha, or wait for someone to approve the account, which would likely slow down the spam, or the fake email addresses would at least have a better chance of being screened.

I understand that the developers haven’t paid much attention to the site since, but surely there is something that could be done to fight this.