Please be polite about sharing machines. Among members, the person sitting in front of a machine has some amount of priority --- it is inappropriate to log in remotely and then use up all of the swap space on a machine thus blowing away the X server --- remember that the person in the office is there answering questions in person and on the phone, and is thus doing something productive.
This is not to say remote usage is not helpful; for example, using the various sipb machines to compile all versions of a given program for the SIPB locker is a reasonable thing to do. Just don't be annoying about it.