At this point, Google hasn't answered (or even been served with) the complaint, so we don't know how they'll defend against the suit. However, the complaint is available online (e.g., here). From my brief perusal, there are a couple of points about it that look a bit odd. For example:
The lawsuit alleges (paragraph 17) that
Google Buzz "posted" to Buzz any information that was previously posted to certain other Google websites, including but not limited to Picasa, Google Reader, and Twitter.Why Twitter is considered a Google website it something of a mystery, especially since Buzz is seen (e.g., here) as an attempt to compete with (among others) Twitter.
The lawsuit was filed in the 9th circuit (specifically, California), which has adopted an interpretation of the electronic communications privacy act which makes it relatively difficult to apply that act to email communications (see, e.g., here).
The lawsuit alleges violation of the computer fraud and abuse act, which is a little odd because that act is generally focused on unauthorized access to protected computers, rather than on unauthorized access to third party data.
Anyway, I suspect that, oddities in the complaint notwithstanding, the Buzz lawsuit will go the way of the Beacon lawsuit before it. That is, it will be settled with the individual class members getting nothing but whatever warm feeling comes from having been part of a lawsuit.* However, while it lasts, the lawsuit could be interesting (especially if Google fights at all), and might provide an incentive for Google to pay a bit more attention to privacy going forward.
*Of course, the settlement hasn't been finalized yet. The terms of the settlement, as well as other information on the Beacon case, can be found here.