tedster - 12:25 am on Sep 17, 2012 (gmt 0)
I'm just guessing here - but I'd say that when lots of pages show up from the same domain that's a sign Google's algorithm doesn't feel there are very many quality results. They'd rather serve up what amounts to the full site navigation than serve something from another domain that they think is a weak result in some way.
I mentioned this in another thread - I've now been hearing some complaint from site owners who lost their multiple listings. No one like losing traffic, that's for sure - no matter why.