They'll send you an email notifying you of your account being closed, and then deny you access to it. When I had an account closed one time, I was already logged in when I received the email and could still view things until I logged out :P.
Normally they will also send you an email warning you that there algorithm has detected something that is agaisnt their TOS and if you want to find out more you cant because of "proprietary nature of our algorithm". I believe this has to do with the way they opporate their business model. If they decided not to patent the way the algorithm works then it is a trade secret which could be very bad for the business if someone found out how it worked. Unless you got an email saying your either doing something wrong or banned I doubt you have been kicked off.