Charging Cell Phone using PC Power Supply

I've been charging my cell phone using a cigarette lighter socket wired into
my computer's power supply, positive connected to the +12V line, negative
connected to the chassis. It seems to be working perfectly.

Is there any reason why I *shouldn't* do this? It's a 250W power supply
running an Athon 950 processor. I only have one hard drive, two CD drives,
and the cell phone connected, so the power consumption doesn't seem to be an
issue. Is there a chance that hot-swapping devices could produce a damaging
surge? If the phone is transmitting, is there a possibility of interference
being generated by the phone, traveling through to the power supply and
mucking things up?