I think that colleges have the right to search applicant profiles on Myspace. If they are made public, there is really nothing to stop them from doing so. I am not saying that it is the right thing to do, but it should be expected if you put your information out there.
As much as I hate to say it, I am in favor of colleges and potential employers having the right to view their applicants social networking profiles. It simply allows them to learn more about the person they are interested in. Not to mention, these are called "public profiles" and are open for anyone to view.