I've recently discovered the same problem. For me, it happens anytime I post from my droid, whether it be from the official facebook app, mobile website, touch website, or full website. I've read countless discussions about it on facebook's "topics" but so far no one has a solution and facebook seems to be ignoring the problem.
If you're like me, you've already checked your privacy settings to make sure you're posting for friends (irrelevant since posting from you PC works), as well as tried to look in the application settings of privacy (the official FB app does NOT show up there, which I think is the root of the problem)
iPhone users have the same issue, but they're allowed to go delete the application's permissions on facebook, for us Android users it doesn't show up. Bloo, a third party facebook app DOES show up there however, and posting status updates from Bloo works just fine. So I think the problem revolves around the app not showing up in the list of applications in Facebook's privacy page. Hopefully someone from facebook will acknowledge our problems.