If you think it's hard to keep just a small handful of people happy, imagine the monumental work behind keeping 250 million people happy. That's one of the tasks that huge social networking sites face on a daily basis, balancing the needs of tens or hundreds of millions of opinions all at once. Facebook has apparently failed in this, to the point that some users have decided to sue. It doesn't take much thought to stumble upon the reason why: Privacy.
Facebook denies the claims and plans to defend themselves against the accusations. The fight itself may not boil down to the wording in Facebook's terms, but rather the process involved in changing it. Part of the suit relies on a claim that Facebook doesn't notify (or notify properly) of changes to the ToS. Though just another suit among many, this is another example of the continuing struggle between users and service providers, battling over who truly owns what.