you keep using that word; I do not think it means what you think it means

I caught a bit of the lawyers' opening press statements in the Dominique Strauss-Kahn case today; I was driving home at the time, with the radio tuned to Radio 4, as befits any sane and civilised member of the human race, when I heard a couple of clips on PM. What specifically caught my ear was the clip of prosecution lawyer Kenneth Thompson, and even more specifically the bit which starts at about 0:17 in this clip, or alternatively about 0:59 in this one, transcribed here:

The suggestion by defence counsel that this was consensual is preponderous - the victim wants you to know that all of Dominique Strauss-Kahn's power, money and influence throughout the world will not keep the truth about what he did to her in that hotel room from coming out.

Now it appears (and this was news to me) that "preponderous" is actually a word (meaning pretty much the same as "ponderous", but with a pointless extra three letters), but at the same time it's clear that what Kenneth Thompson meant was "preposterous".

A Google search for "preponderous" reveals a few instances where it might be being correctly used, but just as many where it's used in place of "preposterous" (here and here, for instance) or alternatively in place of "preponderance", like here and here. Inconceivable!