Over on ESPN's Page 2, there's a great suite of articles on how people can jump to ridiculous conclusions about their NFL teams after only two games -- Chargers are mere pretenders after getting waxed by New England, Shaun Alexander is a chump, etc. It certainly seems more prevalent nowadays than it did about ten years ago.
However, I think the authors should have mentioned the extent to which ESPN and other sports media outlets have contributed to this phenomenon. It seems to me that all this overforecasting took off when the networks started alloting much more time to NFL coverage. There simply isn't very much to talk about when the season is only a couple weeks old, but these television heads on sticks need something to say, so they naturally project the first two weeks' action onto the rest of the season.