Ugh, conspiracy theories again.
Someone mentioned comparing the fuses of TWA800 with a "DC 9 that crashed in the mediterranean". (Itavia, perhaps?)
There's a lot more compelling evidence for that DC-9 being shot down then there is for TWA 800; and even so, I doubt we'll ever conclusively know the answer in the Ustica case.
When that Itavia flight went down, the official statement that it was a bomb was released very quickly, in the days following the accident, and three weeks before the news broke of the Libyan MiG-21 wreckage in Calabria (which occurred sometime before).
When TWA 800 went down, the investigating authorities were very slow to release their findings; yet days after the event, the news that the center tank was on fumes and 50-60 degrees C was included (without hypothesis) in the journalist's reports.
Missiles do knock down airliners, and we have plenty of cases where they do, including missiles fired by the US. The evidence for TWA 800 is just weak; on the other hand, a fuel tank explosion, given the conditions, makes a lot of sense: sure it's a rare event, but thank God we don't have common events bringing down planes very much.
Comparing the Concorde to these things is ridiculous, given the very rare usage of the concorde. Given the rate of failures, if the concorde were as common as the 737 (with its miysterious rudder issues), then several times a week they'd be suffering damage from tire blowouts, including fuel leaks. And once a month there'd be a horrible crash.
Most big explosions happen in Hollywood. Fuel tanks are only at risk for catastrophic explosions when the quantity of fuel remaining (and the heat) is such to create an ideal fuel-air mixture for a spark to set off. A cheap way to remove the oxygen from those tanks is a good thing, even if it's a remote possibility.
Oh and the Swissair MD-11 fire pretty much killed MD-11 production.