He was. They fired (retired) him and replaced him with O'Brien on the Tonight Show...then they gave him his own show, which bumped O'Brien's time slot, so O'Brien so quit. At least that's what I think I remember...i thought Leno was out a couple of years ago? Shows you how in tune i am with late night TV.
I don't actually watch any late night TV, other than SNL, occasionally.
Apparently, it has it's own wiki page http://en.wikipedia.org/wiki/2010_Tonight_Show_conflict