Who's online automatic IP blocker
 

Basically if there are 4 or more ip addresses that are exactly the same, they either get reported to the admin to look into or automatically banned, depending on the users preference. If they are all viewing the same thread, they get flagged with some kind of warning text next to their name.

I've been having trouble with sites like ecatel and most recently server49947.santrex.net among others doing this. I can only find out when they do this by viewing the whos online list so an addon to aid people like me would help greatly. Sure I wouldn't be to concerned about it if I were an average admin but I know that stuff like this can tarnish a sites bounce rate and this in turn can affect search rankings.

Of course have ip whitelists for search bots like googlebot, google image bot, google adsense bot, yahoo bot, msn/bing bot etc.