Throwing mass into a black hole is harder than it sounds. Conveniently sized black holes that you actually would have a chance at moving around are extremely small, much smaller than atoms, I believe. I think they would just sit there without eating much, despite strenous efforts at feeding them. The cross-section is way too small.
To make matters worse, such holes would emit a lot of Hawking radiation, which would a) interfere with trying to feed them, and b) quickly evaporate them ending in an intense flash of gamma rays.
The problem is throwing mass into other mass hard enough to make a black hole in the first place.
Hawking radiation isn't a big deal. In fact, the problem is making a black hole small enough to get a significant amount of it. An atom-sized black hole has around a tenth of a watt of Hawking radiation. I think it might be possible to get extra energy from it. From what I understand, Hawking radiation is just what doesn't fall back in. If you enclose the black hole, you might be able to absorb some of this energy.
This thread is for asking any questions that might seem obvious, tangential, silly or what-have-you. Don't be shy, everyone has holes in their knowledge, though the fewer and the smaller we can make them, the better.
Please be respectful of other people's admitting ignorance and don't mock them for it, as they're doing a noble thing.
To any future monthly posters of SQ threads, please remember to add the "stupid_questions" tag.