Ok, so I'm looking through a list of the school's professors and I see a few that I might like to work with. I read a profile of one of them and it mentions that he is doing something with "his student" and it made me think for a moment... Maybe this is a stupid question, but can professors be "taken", or "off the market"? Are all the professors that are listed on a school's website actually available, or is there a possibility that they already have all the students that they care to handle? Do you have to actually ask every professor that you are interested in whether he or she will be able to take you on if you join the program, or is it a given if they are listed on the school's website?
I can't speak specifically to Business PhD programs, but in Science professors can definitely be at their maximum capacity. It normally has to do both with the professor's time and funding. It is very expensive for a professor to take on graduate students, and most professors are normally limited by the amount of grant funding that they receive. One other issue to keep in mind is that older professors may not be taking on any students if they expect to retire in the next few years. Your best bet is to contact them directly, especially if your desire to join a program is based on one or two specific professors.