By tightening up their minimum thickness requirements, Shapeways has made it more troublesome for designers to upload printable models. Or at least what I got away with three years ago is now being rejected.
But as ghukek pointed out, Shapeways does not cater to their hosted shops like they use too. The marketplace isn't as visible as it once was. The ability for designers to communicate to with their customers has never been improved. And most sales focus on items you upload your self.
As frustrating as it is, I do understand. For years I could host my designs with no responsibility on my part to make them printable. If you bought something that I designed poorly, (which was very common in the early years) and you wanted a refund, Shapeways was out the money, not me.
However, hosting shops is still a large part of their business. My sales have remained pretty constant for quite some time, and I know a few other designers that have not seen a decrease either. They might make it harder on me by being more stringent with their print standards, but I doubt they will ever just close down their hosting services.
And there might be one thing Shapeways might be able to do that no other print on demand or home printer will be able to do. But I will have to wait a few weeks until I receive my test subjects to know for sure.