Registration is PAINFUL
I can't post anything until I've activated anyway, and it didn't like something from the form several times, and each time I had to figure out a hard-for-humans image and type it in.
If I get the image right the first time, STOP BOTHERING ME with it again and again and again until I found a username your system will accept and filled in everything right, or if I've gotten three in a row right, don't bother with the email activation.
You practically need a HOWTO for registering. It should take seconds but takes minutes.
Spam is a problem, but making it painful for every user with a paranoia level of protection makes the cure worse than the disease.