The company has until May 24th to provide info, and Zuck is supposed to make staff available if the committee has any questions.

Facebook hasn't formally responded to the letter as we write this (we've asked it for comment), but it has already denied playing fast and loose with its rules on political objectivity. As it stands, it's not clear that this is anything more than an attempt to court outrage while it's still hot. After all, it's not as if the Senate can dictate Facebook's news policy without running into thorny free speech issues. We'd add that Senate letters only occasionally translate to real action -- this investigation could easily fizzle out unless there's concrete proof of something shady going on.