It seems there was a controversy about existence of more than 1 BH in one globular cluster..
It's a bit surprising for me because there are number of pulsars found in globulars.. so why not BH? (well.. those are pretty massive, but still...)
http://scienceblogs.com/catdynamics/...-holes-in-m22/
http://www.stuff.co.nz/science/77693...hole-discovery
http://news.discovery.com/space/blac...ns-121003.html