Just the GAF (or internet in general) hivemind. Once they get their minds made up about some thing, or game, or service, their minds will never be changed. Case in point: KZ2. Was supposed to be uber-successful, push PS3s, and such, and didn't. Now Scribblenauts is supposed to be this fuck-awesome game and blah blah blah, and people will forget about it a few weeks later for the next upcoming game. Or it's the Orange Box PS3 debacle, where the game was supposedly unplayable, but was actually quite alright. And going with that, it's the hyperbole. Something is amazingly successful, or a bomba. No inbetweens. So because people don't see it as a success, it's a bomba.
But who knows whether or not it will or won't be successful. Sony was able to push the original PSP at 250 @ launch with a much weaker line-up, MUCH smaller feature set, much less coolness factor, much bulkier hardware, and the PSP sold well at that price. I'm sure sony will be able to do much better with the PSPgo