Thanks to those of you who played along and came up with possible endings for this story.
I'll give you the real conclusion now. :)
Just to remind you though, the cabbie and I had been exchanging pleasantries. We were talking about traveling, and our families, and the beautiful weather, when he dropped a bomb in the middle of everything -- "Black people make scary neighbors, you know?" He felt justified in this -- it was his reason for moving recently. He had no idea that this thought would stop our momentum, but my smile quickly faded to neutral as I said, "Really?" He said "Yes."
At that instant, we both stopped talking and sat in silence for about five minutes.