I heard something interesting the other day related to this that I wasn't aware of before but certainly explains why I get almost no calls even from non profits or places I already do business with (have only a cell phone): it's against federal law to use autodialers to call cell phones. The story I was listening to was actually about political campaigns and particularly pollsters being afraid of all the people going cell-only. They mentioned this bit and how they have to dial those calls live because it's illegal to use the autodialer on them.

Pretty good trick, really. Zero calls from banks, etc. even though they have my real cell number and I already do business with them.