Tweetmeme chases links on twitter, annoying pile of...
IP: 18.104.22.168, 22.214.171.124, 126.96.36.199, etc.
Mozilla/5.0 (compatible; MSIE 6.0b; Windows NT 5.0) Gecko/2009011913 Firefox/3.0.6 TweetmemeBot
and more currently on 10/27/2011...
Mozilla/5.0 (compatible; TweetmemeBot/2.11; +http://tweetmeme.com/)
Appears to be hosted on dedipower.com under multiple IP ranges.
188.8.131.52 - 184.108.40.206
220.127.116.11 - 18.104.22.168
More if I get the time, but blocking dedipower's ranges would seem to solve the problem.
One of the reverse IPs pointed to something called datasift.com which claims to be a twitter data mining operation, maybe related, anyone know?