As for black holes...
"Keeton, a member of Rutgers' department of physics and astronomy, said it couldn't happen. He told The Chronicle that a tiny black hole probably could suck up only a few atoms at a time.
Yet it might not go unnoticed. If a black hole as massive as an asteroid -- thousands of tons -- passes through a room, there would be a subtle gravitational tug. "
http://www.sfgate.com/cgi-bin/articl...NGFHJBDE31.DTL