I went throught that plus a bit of the very, very long thread
Here's my .02 from personal experience:
Running a PPC program for a former client a few years back, I discovered through $1000s that Sex.com traffic was simply poor quality/non-converting traffic.
I tried many different setups, tactics, keywords, etc. and gave them the benefit of the doubt for a long time. When I noticed the sales just weren't there, I checked my logs repeatedly and noticed that although the majority of "hits" were coming from a sex.com URL, they in fact were originating from a partner site.
I took some time to hunt down these partners and found some that clearly were little more than "spam" sites (in all fairness, Overture and some other - most? - PPC programs use such sites).
When I asked our rep about this he conceeded that revenue had hit a peak for them and so they had begun taking on new traffic partners - and from the tone of his msg, I took it he personally wasn't thrilled about some of them they took on.
My one suggestion for anyone considering sex.com is to do your research and find out where your links are appearing. Things may have changed (I haven't used them in at least a year and a half), but for me it they essentially became a place to get cheap traffic for toplists, etc. ... and the occasional sale.