Some websites need to do this for various reasons...
1) i.e. To block abusive people on websites. If you've been banned then this stops you simply creating a new login and posing as someone else
2) Gaming sites - stops people creating mulitple logins to cheat
3) To check the number of unique visitors to a webste
4) To track down users involved in illegal activities
5) To impose DRM rights - i.e. stop people viewing content from a different content - say the BBC is broadcasting an FA match on their player then they will block users form other countries accessing it so that the FA can sell these rights individually.
are you insane? that's not the point if it's illegal or not, the point is they use your ip address to taylor the odds! This site has known bugs and glitches plus their customer service is nearly non existant! Coins lost ~ missing yeah lets talk legal!!! maybe thats all good with you...i'd say take a survey of bitcoin users and ask them if they would check the yes box for ip tracking...zzz