If only one part per model becomes enforced, then it more-or-less kills a huge proportion of their customer base. (A
reasonable upper limit would be acceptable, of course; a dozen seems fair - but that is for me, not other folk, of course.)
For one, it will kill a lot (if not most of) the miniatures modellers, myself included: there is no point using Shapeways if it becomes far more expensive than metal. (How can you do tanks, for instance, if you are obliged to do the turret and hull as seperate models?) If you can economically only use it for master creation - well, frankly, there are far better services out there for
that job. There has been a really burgeoning starship modelling community, but Shapeways is looming
very close to losing nearly the entirety of it at it's current rate (as well as getting all the bad publicity fall out).
(And Shapeways cannot be unaware of it, given that they are releasing that 3D random starship generator - though the existance does make it seem like they don't really
quite understand the market there.)
And what about stuff like Oskar's puzzles, which have a reputation enough that even I, someone who is soley interested in miniatures, have heard of? For what I can gather from his shop (without seeing the 3D images, thanks to the delightful new product page) they are either composed of multiple pieces (as a kit or in-situ) or sprued together... And I can't imagine that even if they are sprued they can be easy to clean. (Or does that sort of thing get a pass because it's already expensive?)
At the end of the day, if Shapeways wants to function as a universal 3D printer service, it's going to have to grit their teeth and realise that people are going to want small things printed, sometimes. It's part of the job. Shapeways is in a good position now because it is about the only one who is cheap, and getting a reputation. When it loses that advantage, when other companies start to follow suite (and it's inevitable they will) or the price of the machines themselves and the reliablity comes down (and it's well on it's way, sometimes within the next 2-5 years), there will be no reason to stick with Shapeways if they can't offer a competative service.
(There's already a miniatures company in England that's somehow producing (solid) 1/72nd and 1/144 vehicles at half the price of what it would cost in WSF from Shapeways but with a finish closer to WD. (No, I don't know how they are doing that. I suspect they have access to an industrial-engineering grade machine (i.e. one that does something like Formula One prototyping or something.)). Point is, it's coming steadily.