Is this really that big of an issue? I can see how it can be abused, but I'm sure there are many initial (legitimate) posts by new members that include a link (of some sort). I think the inability to post a link would just prohibit their use and interest in FT.
I see how a post count req. could stifle someone from spamming the forums, but I think that it is better for the Community as a whole to allow anyone to post links. Like you said, the community and the moderators are pretty damn good at policing and taking care of abusers.
And finally, is this even possible in the software? Just my $.02