In the CBS attack, it appeared that the site itself had been hacked and all its content deleted. That wasn't the case. The CBS site was fine. What actually happened was that DNS record for the site's IP address was changed to a fake site that contained a single blank page. IF you'd attempted to reach any of CBS's sub-sites, for a TV show's page for example, you would have gotten only a generic 404 Not Found error message page.
Facebook may be the next target. A video allegedly from Anonymous asks users to attack the popular social Website on 12:00 AM EST on January 28, 2012. No real reason for attacking Facebook is given, save "To show them indeed that we are not, playing." Attackers are encouraged to use DDoS programs for this assault.
However, there have been false claims before that Anonymous was going to attack Facebook. With no other reason than to attack Facebook than to show that it can be done, and with issues more important to Anonymous supporters such as the Megaupload takedown and ACTA demanding action, I suspect the Facebook call to arms is a hoax.
That said, sites that do have a stake in issues that Anonymous care about should continue to keep their DDoS defenses on high. As the last few days have shown, any site can be taken down by a sufficiently powerful DDoS attack or side-lined by DNS poisoning.