Interesting points. PoE would be a special case. Using the first chart google points out [
link], 100m of 24AWG (worst case, cat6 is supposed to be 22) wire would have 8.41976ohms of resistance. (PoE uses 2 parallel pairs.) 802.3af specs 15.4W (350mA) and 802.3at 34.2W (600mA.) So, a max "af" device would have just over 1W in the cable, and "at" just over 3W. If you put 48 runs in one conduit, they were all pulling full power, and they were all 100m... (an unlikely case) that would be a 50W or 146W pipe. (31 and 92 for 22AWG) That'll get toasty if there's no air moving around it. (BTW, I've seen power conduits like that, but never any data wiring.)
[PS: It's worth noting your switch or midspan would need a 750W or 1700W power supply *just for PoE* to run such a setup.]