It's an "every man for himself" attitude these days, particular among small and medium sized adult companies.

The heavy hitters make all kinds of mega deals like the one you pointed out, but it's such a small portion of their activities, it doesn't matter much.

There was a period when sites were actively trading banners, signing up for each other's affiliate programs and such, but that's long gone. I've only had one or two requests to exchange links in the past year. If anyone contacts me personally it's always to send traffic to them with no reciprocation.