I don't think the usual rules apply here. Googleguy didn't step in (WMW) for nothing, as Nintendo pointed out here in another thread...
My main* (old) sites are all still in the main index, and Google added loads of robots.txt-blocked pages too (url only on the
serps). My sites are all very different in style, code and shade of grey. A couple of darker pages got magically re-included hehe, title and description and everything.
But I can't see a pattern yet...
* example: witless.net