Mr. Fred Wilson brings up an interesting point that product promotion is also changing nowadays. Blogsphere is very powerful and many companies, (even big ones like Google) are promoting their new products (even those as revolutionary as OpenSocial) through these streams over the more traditional big media event shows.
Bloggers tend to target a niche market for themselves and they have readers with the same interests. Therefore, by reviewing they are in fact breaking up your product into pieces and each emphasizing on what they find most interesting (taking their niche into consideration). Therefore, the readers learn about the new product and the features that would be most interesting to them, in a language that they can understand the best.
It is as if a company is hiring a huge team of PR and is getting them to do customized/personalized promotion of the product for many different groups of people.
And keep in mind that this is happening at very low costs and is possible to be done by any company at any size and budget.