>> Yes, but they can make public posts?! They've earned no trust, why do they have this main privilege?
Yes, I do allow new members to post without moderation. Thankfully, the country- and content-based filters I have applied automatically filter posts. This works woderfully with the exception of some persistent spammers every now and then targeting my userbase demographic specifically. We have a high turnover rate because of the topics we discuss; meaning if a user is moderated, there is a high chance they won't continue discussing the topic (current events, mostly).
>> Do you delete accounts that aren't contributing to the forum? What's your policy on lurkers?
I don't. The reason being is that forum membership and site membership go hand-in-hand. Users don't get access to certain functions not related to the forums if they aren't signed in. Users with unconfirmed email addresses are eliminated after a period of time and also don't have access to anything except a notice regarding email confirmation.
But back to the main topic: To combat these profile spammers, I've had to take the unfortunate step of completely removing web sites from the "edit profile" pages. I really hope this will cut down on the bogus registrations when they figure out they can't add urls. They obviously didn't realise that we don't even include urls on profile pages to begin with.
Most of these clowns seem to have a user-agent identifying as Firefox 3.5.6.