Yes, the Malaysian government, et al. have been withholding information.
According to a BBC report (that no-one else seems to have picked up on yet), we do have hourly pings from Inmarsat, and they show the aircraft flying more or less due south. The theory now is, essentially, that the aircraft turned west after its last waypoint, flew to the vicinity of Grand Nicobar Island (that small dot just off the northernmost point of Sumatra), and turned left.
Back to the map (originally from a contributor to the blog Luchtzak Aviation, thanks Luke). Flying due north or due south at this point does us a favor from a geometry standpoint. Rather than crossing the Inmarsat arcs at an angle, the signal would sit on the same arc for a while. I don’t have the tools or the time to mark up this map, but you can imagine from looking at the one arc we have, how successive pings would tend to stay on the same arc.
It gets better. The aircraft was north of the equator, and so a southerly track would stay on the arc longer, as it passed abeam of the satellite position. Also note that a southerly track from Grand Nicobar (nothing significant about the island, it’s just a good reference) would hit fuel depletion at about the same time as the last detected ping. A northerly track would not, and would require that the aircraft would have to do some maneuver that would have it on the northern arc at fuel depletion — that maneuver would be apparent by the fact that it crossed different ping arcs.
So, the theory that best fits all the facts right now is that the aircraft shut down its communications, flew via waypoints to somewhere NW of Sumatra, turned south, and flew until it ran out of fuel.
Tags: flight MH-370