so cal lurker wroteMe thinks that many of the responses you get are going to depend upon the picture the reader builds from the words. It seems to me (not a ref) that the details on the contact are going to matter a lot here on how they tangled. If the blocker was going up and over such that there was no way to block the shot without subsequently wiping out the shooter, I think that is pretty easily a foul. If there is minor contact from two players who fall because they are running at speed that seems to me not a foul. And there is a whole lot of grey in between those.
Agreed.
I'm in the camp that is more likely to pass on a foul that involves a clean block up top with some contact below but this is a HTBT situation.
I will say though that the fact the play from the defender "from behind" makes it more likely that I have a foul on this play.
But again tough to say with out seeing the specific play in question.
ETA- And as others have suggested, the level of play is also a significant factor here. With bigger and more athletic players you are going to see, and assigners and coaches expect, more contact to be deemed marginal or incidental.