tedster - 4:13 am on Dec 14, 2012 (gmt 0)
A couple impressions here - these are definitely not conclusions.
One factor that seems to work for a month or two is freshness. Fresh pages often rank well with almost no backlink support. However, that doesn't create a sustained effect.
I also think the query phrase itself is a factor. It needs to be a pretty strong phrase for it to get the "full treatment" from Google's complete algorithm - especially in the trust/authority area. Google doesn't call their semantic component "phrase-based indexing" for nothing.
We saw this when Panda first rolled out and then, according to Google, it was later extended further down the long tail. Now where that threshold might sit is another question.