My friend a lot of the posts related to this had been posted.Please visit the one for your answer.The one post which I remember is the one posted by Pioneer0333 on 01/06/06 03:24 PM.This u will find probably on 3rd page of the forum
Collissions are rare in the Universe. Black holes are much smaller than planets (except the super massive black holes) so a near miss is a trillion times more likely than a hit. Likely zero black hole collisions have occured in our galaxy in the last two centuries, and collisions in near by galaxys likely release less energy than we can detect that far away. Neil