http://www.websense.com/content/URLCategories.aspx
"Social Networking - Sites of web communities that provide users with means for expression and interaction."
Funny they included 4dots.com but not mobileread.com. Really strange in fact, since there is nothing on 4dots.com. Hmmm. I'll look into it. Maybe if it's not too much work I could implement a setting in the User CP allowing for these cases to have the static content served from a .mobileread.com domain. No promises yet.