The main hurdle that plaintiffs in privacy lawsuits encounter centers on the difficulty of proving damages. Simply revealing information about another isn't seen as causing injury -- at least not the kind of injury that courts compensate people for.

Facebook now is arguing that a potential class-action lawsuit against it for having changed its privacy settings should be dismissed precisely because the members who are suing haven't alleged any tangible injuries. "Plaintiffs fail to make a single factual allegation that specifies what information, exactly, Facebook has allegedly improperly disclosed or that Facebook publicly disclosed information that any Plaintiff intended to remain private," Facebook argues in papers filed last week in federal district court in San Jose, Calif. "Instead, the complaint relies exclusively on vague, generalized allegations that say nothing specific about the named plaintiffs or how they have been harmed by Facebook."

Even though the lawsuit alleges that Facebook exposed members to the risk of identity theft, Facebook counters that people can't sue for such speculative potential injuries.

Facebook sparked a round of complaints last December by changing some of its default settings to "share-everything." In April the company made another set of changes, including launching the controversial "instant personalization" program, which shares users' names and other data with Yelp, Pandora and Microsoft Docs. Users can opt out, but if they don't do so their information is shared by default.

Facebook revised some of its privacy controls recently, but not all of them. For instance, instant personalization is still an opt-out program.

Even if a court decides that Facebook's policies are problematic, the company could well end up winning on the ground that it didn't cause members to lose money or suffer any other economic injury. But even if that happens, Facebook is likely to still face pressure from lawmakers and advocates -- not to mention the Federal Trade Commission.

Besides, even if Facebook members can't successfully sue for privacy violations, they can do something potentially more powerful: They can stop visiting the service. Facebook reportedly is ready to announce that it now has 500 million members. But if those members don't repeatedly return to the site, their value to Facebook is limited. And with new social networking options in the works, Facebook could decide it's in the company's interest to rethink its approach to privacy.

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