"...there is bound to be some government employee who states emphatically that it is NOT terrorism..."
TWA 800 comes to mind - terrorism? Or just an errant missle from a US Navy ship?
Explosion of the center fuel tank Id say. The conspiracy theory is assuming a MANPADS brought down this plane. Firing from sea level up to 13,800 feet at a target that is moving 300 knots (IAS) is stretching it for a MANPADS of ANY type (SA-7,14,16,18, Stinger Basic, Improved or even RMP. Stinger LR was not around then). Many of the older MANPADS can only get an aft shot anyway and those are completely out of the question. Waiting until the target passes over and then taking an aft shot on something that high and fast which your little missile now needs to climb up to and chase the whole time is not feasible. SA-18 and Stingers can fire all aspect, but where can you get one of those (And even they would be over taxed)? Despite all the conspiracy theories, we keep good track of certain weapon systems, as does everyone else.
http://www.globalsecurity.org/military/systems/ground/stinger-specs.htm
Look at last page IAS and Altitude.
http://www.ntsb.gov/events/TWA800/exhibits/Ex_10A.pdf
Other problems with this theory is that there would be remains or pieces of the missile left in the wreckage. A small MANPADS has a relatively small warhead and several airplanes have been hit in the past and survived (http://www.washtimes.com/world/20031123-123323-6531r.htm or http://www.telegraph.co.uk/news/main.jhtml?xml=/news/2002/11/29/wkenya29.xml).
The crew might have seen the missile coming. The wreckage should show signs of a blast and have residue that can be detected with a mass spectrometer. We talking about .00001 gram. Equipment that is so sensitive that it can pick up explosives in your sweat for weeks after you touched it. Explosions leave traces. (http://www.geindustrial.com/ge-interlogix/iontrack/prod_vaportracer.html).
It is extremely unlikely that the popular terrorist idea is accurate. There are too many holes in it for it to even be remotely feasible.
Red6