Well, I heard it again today on NPR: the noun troops with a cardinal numeral. And this time with the smallest of all non-singular cardinal numerals: among the dead in one incident in Iraq today were two American troops, they said. Well, I'll tell you how that noun is in my variety of English: it's a plural-only noun that doesn't take cardinal numerals. it's like alms, auspices, credentials, folks, genitals, odds, particulars, and lots of other such words listed in  on page 343 of The Cambridge Grammar of the English Language and discussed on pages 343-344.
I'm not prepared to say there's a mistake on anyone's part involved here, because some of these nouns show a bit of variation, but I'm surprised at the way this is catching on (I believe I have heard the usage from President Bush, which may explain the way journalists are picking it up). To me, troops is a grammatically plural way of referring to soldiers en masse (Support our troops), it's not a semantically plural version of a singular noun. For me (and NPR increasingly seems to differ), you can no more have *37 troops or *two troops than you can have *one troop — except, of course, when you're using the different lexeme troop, which means a whole group of soldiers or Boy Scouts or whatever. I can certainly accept Two troops were killed as grammatical if it means two troops of Boy Scouts, which (under the Boy Scouts of America rule that a troop must have at least five Scouts to merit its scoutmaster) implies at least ten fatalities. But if a troop of American soldiers in Iraq loses two brave men, that's two soldiers, not (mercifully) two troops. That's the way Standard English is for me. Your mileage may differ.
[Additional notes: Glen Whitman of Agoraphilia wrote about this topic last year (click here and scroll down a bit). He cites this article, in humorous mode, by ranting, tights-in-a-twist journalist Debra Lo Guercio. And Antonio Fortin has pointed out to me that the March 2003 issue of The Onion appears to take my view, giving the joke headline "Kuwait sends troop" illustrated with a lone Arab soldier in a desert.
Stephen Neale points out to me that I may be a bit hasty in saying there are two lexemes here, and I agree with him. There should be a way of saying that there is one polysemous lexeme with limitations on how you can use its singular.
Finally, Arnold Zwicky remarks that "Geoff Pullum complains...", but it seems to me that I make no complaint at all above, I merely note (admittedly, with some surprise) the increasing pace of this shift away from my own dialect on this point, and away from Standard English as The Cambridge Grammar cautiously attempted to describe it (with caveats about the possible variation). No complaints about such shifts will be heard from me (see Lo Guercio for that). I hold to the New Hampshire principle of natural languages — that a language has to live free or die. Which is not the same as the notion that anything goes, by the way. Standard English as used on NPR and in serious Anglophone newspapers has correctness conditions; and on the small point of how troop is used, those conditions seem to be in flux right now.]Posted by Geoffrey K. Pullum at February 25, 2005 12:58 AM