There have been numerous reports on Twitter and other sites of these and related problems. Officially, Facebook had nothing to say on its press page or its Twitter feed. A Facebook respresentative said after the firs hours that "Earlier today, we experienced an issue that prevented some people from loading Timeline or Pages content for a brief period of time. We resolved the issue quickly, and content is back to normal. We're sorry for any inconvenience we may have caused."
The problem appears to be with Facebook's internal integration of databases rather than a Distributed Denial of Service (DDoS) attack or any other external problem. We still don't know exactly what went wrong. This partial service disruption comes only a few weeks after a more serious Facebook outage.