Everything I've seen about wood bees says that the males do not sting or bite (they are the ones with the a white spot on their face, although some sources say the spot is yellow) but the females -- with the black faces -- do. That must be the reason for the occasional stories of being bitten. But I'm not sure I'd want to stick around to have a look at a bee's face! (Right, Shelly6? ROFL!) Apparently they bother you most in their "home territory."

Sometimes several bees will use the same hole and have several tunnels branching off of the main one, and tunnels can extend several feet into the wood. The sources I consulted recommended treating each hole found with an insecticidal spray or dust. I don't usually like to suggest chemicals, but I can't see any other solution if you have a big problem. What you do is treat the holes, then plug them with wood putty so the bees don't re-use the tunnels or overwinter in them.

It wouldn't hurt to keep hairspray nearby when you are working outside to spray attackers.