If there was a tail side explosion, most likely it would be in the area just below the section we've seen (check the side by side pics, there's about 10' of tail below that blue A and the section pulled from the bay pretty much ends at the blue A), but you'd expect our bay section to be splayed on the bottom and possibly torn. Instead the bottom just looks like it got removed, you'd almost expect to see the rest of the plane under it the thing is so clean.
Like all crashes there are a lot of wierd anomalies in this one. That's typical, no theory ever matches all the evidence in something as complex as a plane crash, it can't. Right now none of the sabatoge theories are holding up any better than the mechanical failure theories (well the mysterious metal eroding liquid theory seems to be doing pretty good, except I've seen no documentation that it really exists the way some futurists (aka sci-fi authors who can't come up with characters... sorry never had much respect for that profession, according to them my car should fly, it doesn't I want an explanation) say it "does". Obviously there's corrosive acids that do all the same damage, but don't pass the undectable muster.
Basically we've got 4 probable locations for the damage to start: tail fell off, engines fell off (that's 2 places, one for each engine), "underarm" (wing coupling) fire. None of the theories (sabatoge or accident) can manage to cover all 4. Even given what we know about the massive colateral damage that happens when parts fall off a plane (DC10 in the 70s, Air Alaska not long ago) it's hard to see it snowballing to all the other damage the way this plane went down. That right there is good evidence to sabatoge, but that would also indicate a pretty severe level of overkill and terrorists usually aren't that thurough (quadruple redundancy is a NASA thing, not an Al Qaeda thing).
Subsequently it's all wide open, and the NTSB is still the best accident investigators on the planet. We should stop harrassing them and let them do their work. If they're lieing to us we're SOL, and in general it's a non-political organization (not counting the Clintoon years, everybody was political then) and do good work.