John Gruber points out that Google Chrome OS is vaporware. There’s no running code, there are no devices, and there aren’t even screen shots. He asks but doesn’t answer why Google made this announcement right now. Steven O’Grady punts on this question in his analysis as well.
This is the burning question for me, why now? In the olden days, we’d call this FUD. There are not many reasons to announce something so early. One is that it was about to leak, and Google wanted to get its story on the record before the media took off with the story. The other is manipulation (FUD). You announce something early to keep people from making decisions without taking your future plans into account.
Right now the market share of the Chrome browser is small. That gives Google little juice in terms of demanding a seat at the table in discussions of future browser development. Google may be trying to raise the prestige of Chrome by letting people know that soon there will be computers available which will support Chrome and only Chrome for browsing. If people presume that Chrome OS will be successful, then suddenly it becomes much more important to take Chrome into account in the overall browser market. So that’s my guess: Google is announcing Chrome OS so that more people will take Chrome seriously.