I have something weird to share:
During the course of testing IP MP cameras without a suitable infrastructure, we were provided with Vigitron Vi2301/Vi2316 evaluation units to transport the stream from an IP MP camera approximately 600 feet. We were unable to get the camera to power up and found that the Vi2301 and Vi2316 devices will not provide POE over a single pair. We learned that both the Vi2301 and the camera needed to be powered at their locations. Since the camera we tested was POE only, we would have had to power the Vigitron with 24VAC or 12VDC and add a POE inserter for the camera.
The really strange thing is that when presented with the problem, Vigitron provided two Vi2401's with coax-to-UTP converters (basically baluns with, I believe, the transformers bypassed). Essentially, the coax-to-UTP converters just changed the connector from a pair to a BNC.
The biggest shock was that this Rube Goldberg setup actually works! We are getting reliable POE power for both the camera and the Vi2401, plus 100Mb/s data transport over an approximately 600 foot length of a single 24 gauge pair of Cat5. Total draw of the two devices (Vi2401 and Axis P3364) is supposedly 14.6W (12.1W for the P3364 and 2.5W for the Vi2401). This flies in the face of everything I learned about electronics in over 40 years.