[Washington Post]- At the beginning of last December, Ning reversed course on its anything-legal-goes policy by declaring a prohibition on adult social networks.

The reason? Porn wasn’t paying the bills; instead of attracting advertisers, it was scaring them away. Legal adult content was also begetting illegal content, which drew the ire of both authorities and lawyers with DMCA notices in hand.

Given the report released by CPM Advisors at the beginning of 2008, which suggested that Ning relied on adult content for much of its traffic, one might expect Ning to take a hit after shooing the smut out the door. But according to comScore traffic from January, that hasn’t been the case at all.

Ning gave adult networks until January 5th to pack up their bags and leave. That gives us the rest of the month to see how the network of networks fared without them. And it actually fared quite well, picking up almost 1 million unique visitors in the United States (from 3.94 million in December to 4.79 million in January). That pickup is almost enough to pass Bebo, which attracted 4.97 million Americans in January and barely managed to halt a downslide that surely didn’t make AOL happy.

What’s not clear is whether there’s been much dispute over what constitutes adult content. As far as we can tell – and as CEO Gina Bianchini outlined prior to the evictions – Ning hasn’t prohibited nudity entirely. Nudist social networks are still listed in its directory, for example, although all of them appear to be private networks.