Physical Security...What's IT's responsibility?

Hello Spiceheads,

I'm trying to figure out the typical division of labor between IT Pros and Physical Security Professionals.

In your experience, what percentage of the time does Physical Security responsibilities fall to IT as far as making the purchasing decision and/or supporting the technology?
Are there particular industries or company sizes where the responsibility for Physical Security falls to IT more often?

Do you find that any of these categories tend to fall to IT more often than others, Intrusion Protection, Fire Detection, Video Surveillance, monitoring, Access Solutions?