Here's the US Transportation Security Administration itself had to say about the limitations on liquids carried onto planes as a result of the threat of binary explosives:
The preparation of these bombs is very much more complex than tossing together several bottles-worth of formula and lighting it up. In fact, in recent tests, a National Lab was asked to formulate a test mixture and it took several tries using the best equipment and best scientists for it to even ignite. That was with a bomb prepared in advance in a lab setting. A less skilled person attempting to put it together inside a secure area or a plane is not a good bet. You have to have significant uninterrupted time with space and other requirements that are not easily available in a secured area of an airport.
So, in other words, even if a terrorist could get materials past a security point and try to mix them, even in ideal conditions, they're unlikely to produce an explosion.
As usual, things seem to be more about the appearance of security rather than security itself.
(HT: Slashdot)
