there actually ARE real fighters who post on sherdog, even the one and only Bas Rutten has appeared there a few times (after his WFA fight). Notice the section called "Ask The fighters"? it is there for a reason, there is even one thread, where Enson "Yamato Damashi" Inoue contacted a poster on sherdog forums, they scheduled to meet, had a "sparring" match and Enson tore up the fans face..but now Enson considers him family, and they party and train together. There is a VERY long thread regarding all this, and Enson remains an avid poster to this date ( along with many other fighters ) on that forum.
Link to the Enson thread - http://www.sherdog.net/forums/showthread.php?t=275935
Its easy to tell who is a pro fighter, and who is a regular poster.
Underneath the names, it says "Proffessional Fighter", with no stupid belt in the avatar like they have on sherdog.
Here is even a link to a list of all the current fighters who post on sherdog.net- http://www.sherdog.net/forums/showthread.php?t=342446