rowan194 - 9:32 pm on Aug 28, 2012 (gmt 0)
Cheers for the tip - just tweeted a unique URL on a very quiet domain and noted there were a few IPs that hit the server immediately, all within the space of 5 seconds. (agents: TweetmemeBot, UnwindFetchor, Twitterbot, Butterfly, "JS-Kit URL Resolver")
I presume these bots must subscribe to the realtime twitter stream, with the follow-on stragglers periodically querying the public API to find new URLs to munch on.
I've never used Twitter before, was just interested to see the bot activity.