How Mark Zuckerberg's testimony lurched from easy ride to headache

Facebook founder was lost for words as representatives asked questions about user tracking

As Mark Zuckerberg left Congress on Tuesday after testifying to the Senate, he may have felt relieved. The four-hour Q&A session had been largely dominated by mundane questions of fact about how Facebook works, requests for apologies and updates he had already given and was happy to repeat, and shameless begs for the social network's cash pile to be used to expand broadband access in senators' home states.

Less than 24 hours later, however, a very different pattern of questioning in front of 54 members of the House of Representatives suggested a much more worrying outcome for Facebook - that this could be the week its crisis moves from being about mistakes in the past to inherent problems in the present. Perhaps, the representatives implied, Facebook doesn't just have a problem. What if it is the problem?