According to Wikipedia:

A black hole of one solar mass has a temperature of only 60 nanokelvins; in fact, such a black hole would absorb far more cosmic microwave background radiation than it emits. A black hole of 4.5 × 10²² kg (about the mass of the Moon) would be in equilibrium at 2.7 kelvins, absorbing as much radiation as it emits. Yet smaller primordial black holes would emit more than they absorb, and thereby lose mass.

http://en.wikipedia.org/wiki/Hawking_Radiation

Another thing. What does it mean to say that a black hole has charge? Does that mean that if ia BH were to pass one of us by then the associated magnetic field would allow us to extract energy from it's momentum?

And another thing. As mass gets closer and closer to the event horizon it gets red shifted more and more, and an outside observer never actually sees mass pass the event horizon. So that means that an outside observer will never see the black hole gain mass - so it will appear to remain as massive as it's birth weight. So when we see a 10 solar mass BH it must have been that when it was created, and when we see a billion solar mass BH it must have been that when it was created. Granted that if we include the area around the event horizon as part of the BH then we could say it was gaining mass, but we could not say that the event horizon was changing in location because an outside observer would never experience anything passing it (which would be required if it were observed to grow).

I've wondered about these for years. Is it because my model is not sophisticated enough due to my limited knowledge of physics ? Probably.