In a post by 'Hindrocket' on PowerLine, I read this interesting quotation from David Kay's report on the search for Iraqi WMDs:

We have not yet been able to corroborate the existence of a mobile BW production effort. Investigation into the origin of and intended use for the two trailers found in northern Iraq in April has yielded a number of explanations, including hydrogen, missile propellant, and BW production, but technical limitations would prevent any of these processes from being ideally suited to these trailers.

It seems to me that the ambiguity of the evidence is itself quite sinister, though perhaps not sinister enough to stand up in court. Why would a trailer be partly suited for several jobs, but not ideally suited for any of them? Unless someone can come up with a job for which it is ideally suited, the most likely explanation is that it was designed to be multi-use, specifically to combine an ostensible harmless use (e.g. filling weather balloons) with an actual malevolent use (e.g. biological warfare). To take an example: A sword-cane is likely to be less useful as a weapon than an ordinary sword, and less useful as a support for the weary than an ordinary cane: it would be too skinny for the one and too heavy for the other. The only reason to carry one at all is deniability: a not-very-good sword which everyone else thinks is a not-very-good cane may come in handy in a fight.