I agree that Drexler won the debate (or at least that aspect of it), mainly because Smalley overstated his case.
I think the grey goo argument was directed against Drexler not because of his 'mechanical' approach to nanotechnology, but because of his claims that it would produce replicators that are far faster and more efficient than biological ones.
Errr, I don't know who came up with the concept, but it was prominently featured in Engines of Creation by that name.
It is a legitimate concern, but a few years later, when the nanotech conference was at MIT, I remember him saying that it looked easily solvable for the good guys, e.g. make assemblers depend one or more chemicals not found in nature in significant quantities. The problems of bad actors, well, no one has any better solution to them than we've ever had.
That's one of the problems I see with the chemistry etc. community's suppression of nanotech development. The first entity that both develops nanotech and decides to take over the world will do so unless we get our act together (something he's mentioned as well, I think in Engines).
I think the grey goo argument was directed against Drexler not because of his 'mechanical' approach to nanotechnology, but because of his claims that it would produce replicators that are far faster and more efficient than biological ones.