I've noticed in my own stats, as well as searching on other sites, a fair amount of traffic that comes from urls that look like this:
Which looks a lot like a valid stumbleupon referrer, but from a bogus domain. 'wwwstumbleupon.com' is not running a redirector themselves there, so I'm guessing this isn't something nefarious from the owners of that domain.
Does anybody know if this is valid traffic from stumbleupon? Perhaps from a beta version of their toolbar or something along those lines?