[Suicide Junkie]

Originally posted by Slick:
Also, there are theories that allow for the creation of black holes by mechanisms other than stellar collapse. These other mechanisms could produce black holes of quite small mass which would have very short lifetimes relative to the age of the universe.

Slick.

There are also potentially "primordial black holes" which would have been generated about the time of the big bang at a variety of sizes...
As such, they'd evaporate at various times, and might be visible from the burst of radiation as they die.
Too close, and they'd irradiate the solar system killing everything, of course, so there is an upper limit as to how many could be floating around.