USB spec is 500mA @ 5 volts = 2.5 watts (or better), which not all devices meet but most exceed. It takes between 2 and 6 watts to power a 2.5" drive/enclosure, most of them are around 3.
So that is a roundabout way of saying I agree with you, it would be nice to see what the port actually outputs. I would expect over 5 watts.
Here's power consumtion for a bunch of 2.5" drives:
http://www.tomshardware.com/2008/01/...r_requirements