The number I post online (for instance,
here) is a google voice number. If it becomes a problem I can make it not ring any of my real phones and simply collect the messages later.
One could find my home phone number relatively easily (check out the whois of any one of my domains). My cell phone would be a bit harder, but I don't really protect that much either.
But I've posted it all over the place and I've only ever received one phone call from an internet person. I was too boring though - it was a very short call.