PS/2 is not hotpluggable. It is possibly to short-circuit your motherboard and fry your controller (not likely, but I saw at least one broken mobo after a failed hotplug attempt)
No, at worst you would destroy the fuse. That is why the fuse is there after all. Most decent mb's have healing fuses on those ports anyway.

The best part about PS/2 is that it is assigned its own interrupt and does not have to share with anything else. Frequently you will end up having your USB controller shared with your video, SCSI, etc, and thus causing more latency whenever a USB event arrives. With PS/2, it's the mouse, and just the mouse, on that interrupt.

Score:4, Informative