IMHO 3 days is a lot.
If I had had to wait 3 days, I'd never post just like I've done with hydrogenaudio.
Currently another board I visit has a similar problem with fake registrations. They decided to add a trap to the registration process : the website field must stay blank otherwise the registration is silently dropped. Of course, this field can be changed in the user's CP (there's a notice right to the field during registration). There's also a website keyword blacklist.
And last, something I've forgotten.