Most campuses block it because 1) It eats up a lot of bandwidth, which is expensive for them and 2) 99% of the traffic sent across limewire is illegal and/or infected.
oh good god. while you are connected to the college campus's internet, do NOT use limewire unless you want to get in trouble. if you're using your own internet then thats another story but they can link you from it and that is the easiest, stupidest way to get in trouble.