A Bot from Brussel?!

I can see in Google Analytics a bunch of new visits every day to our service, buzzbox.com, from Brussel, Belgium.
They don't look right. It seems to be a Bot that is somehow downloading all static files and executing the google analytics script too.

All the visits come from 2 IP addresses

84.17.129.60
84.17.129.61

And the User Agent, as it appears in my access log, is

"Mozilla/5.0 (X11; U; Linux x86_64; c) AppleWebKit/528.5+ (KHTML, like Gecko, Safari/528.5+) WebShot"

We get most of our traffic from Twitter, so I think it is something connected with Bit.ly

I'm currently blocking requests from those IPs... but it would be nice to understand more. Anybody has any clue? Please leave a comment.