This isn't news. Does anyone expect the US Army to conduct arms Kote checks of the IA and IPS? Oh, sorry, this is the BBC, so I suppose they do.
We have handed out a fair few tens of thousands of AKs and pistols in the SE, and I bet we've no idea where they are either, nor would we expect to. What they do with them is their concern - and if lots have been used against us, well, that's depressing but again surely not unexpected.
Meanwhile I presume that all the SLRs we gave to the Sierra Leone Army, and all the other weapons we've given away/sold over the years are fully accounted for as well? And the Russians and Chinese have I'm sure kept flawless records of all those AKs and RPGs?
Still, it's an easy stick to bash the Yanks with, though.
The point is firstly the scale of weapons the americans have let go of. This is a lot of weaponry, enough to give every British Soldier an AK-47 with spares. These weapons were meant to go from A-B-C, but somewhere around B they went walkies.
It's not a case of, "I can't believe the US are supplying weapons..." but more a case of, "I can't believe the US can't get these weapons to where they're meant to be..." as a whole bundle have simply been lost in the ether (read insurgents).
Everyone should be aware that weapons are sold and bought regularly, the problem is that the US has been irresponsible in distribution of said weaponry. They should have kept tighter control.