Projected winners an hour after the polls close?

Is it just me or are some of these projected winners coming awfully early? Bob Casey has been projected as the winner in Pennsylvania already and only 3% of the precincts have reported. He may very well defeat Rick Santorum, but it just does not seem statistically responsible to call that race yet. I'm sure they are factoring exit polls into their projections, but those have hardly been reliable the past couple of election cycles.