Is it acceptable for a student to connect with a professor on LinkedIn? Earlier in the semester, I was informed by both an advisor/academic counselor and a professor at my university that it is a good idea to connect with professors on LinkedIn if they have interests in the same area as me.

I sent a connect request to one of the professors I had last semester (along with some other profs, most of whom accepted) and he just wrote back to me saying it is extremely unprofessional to be trying to connect on LinkedIn for a student/prof relationship. I am confused - how is this unprofessional and how can this be handled better in the future?
It sounds to me that this is just the reaction of that particular professor, and so there's not much you can do about it. Perhaps the professor only likes to use LinkedIn to connect with other researchers and professors, but personally I don't believe that it's unprofessional or inappropriate for university students to connect with professors. You are both adults and the site is intended for networking in the professional context. I myself added many of my lecturers on LinkedIn while I was an undergraduate, with no problems.

If you'd added him on Facebook, that might have been a different matter, as many people want to keep their work and personal lives separate and would regard such a friend request as overstepping that boundary. However, all you can do now is move on. In the future, perhaps only add professors that you have got to know quite well, as then they will recognise you if you request to connect, which in turn will hopefully mean they are less likely to refuse.