[justbondage]

Length does matter (har har har) thisismypornsite.com will not be looked on as favourably as pornsite.com.

Also from a word of mouth point of view, the shorter the better.

I am not sure about hyphens with regards to search engines, but I know that most users will type in a site without them faster than they would with. So if someone said to someone in conversation - go to sex-blog.com they would probably go to sexblog.