The danger in using such a meta tag, I believe, is in relying on it. If you believe that the tag is all you need to optimize a page for an organic geo search, then you most likely haven't done your job.
I think in most situations you need to really think about possible vocabulary for a geo-search, and figure out how to optimize a page or a site for various combinations. It's often not easy.
This does pull me into the discussion. ;)