Trade shows are expensive to pull off and even big ones like CES hit just a minutely small percentage of the buying public. Yes it's a way to get exposure in the blogosphere but you're fighting for space on Engadget, etc... with everyone else at the show. In the automotive and motorcycle industries, manufacturers are scaling back or not going at all because of these dynamics.
For a tenth of what CES costs, Pentax could ship 100 K-x and K7s to influential bloggers next week for evaluation. They'd get favorable placement on blogs (it'll be a slow, post-CES week).
For a hundredth of what CES costs, Ned Bunnell could fly to DPReview's offices with a 645D prototype and get as much press.
Blogs and discussion groups like this have changed the economics of marketing. Going to trade shows doesn't always make sense, especially with limited marketing dollars.
Besides, don't you want Pentax to save up for their Super Bowl commercial???