Have you ever sat in a college class and listened to the lectures without paying?

i go to community college right now and all the class rooms are really small. yesterday i went to a humongous university and walked into a class to hear a lecture. The rooms are big i sat in without being noticed. i went to a couple of more and really enjoyed my time there. oh and there was plenty of room i didnt steal anyones seat. anyways i dont know how many times i can do this. id like to take a friend whos been out of college for 2 years now and bring him to one of these lectures to see if he can still tolerate school. Can i keep doing this? have you ever done it without getting caught? if you do get caught will i be banned from the school?