
I have noticed a trend in the last year for these "datacenters" to go through all the captcha and then post something innocuous like "Wow this is a great site. I hope to learn a lot here."
One today put "Islamabad" as his city. Wow, maybe he is a spammer?
As I watch these guys, over a few weeks there will be maybe a dozen or more signing up with the same IP. Then, at some point when they are all in place, you get the spam floods.
I think I am going to create a new member category called Spammer that has no posting or other privileges. I'm tired of deleting these jokers and would rather give a little back. Instead of deleting the account and/or banning, maybe that would at least be more fun.
I don't like manual approvals. If you put yourself in the user's place, they are signing up because they want to post in a forum (or whatever) right now. I don't want to put that enthusiasm on hold.