yeah not a fan.
chrome is currently a conduit for numerous viruses - my main objection to chrome itself.

But I can see thingiverses point.
Nothing to stop anyone downloading an .stl file and then getting it commercially printed. But not sure I like tying it into a single print service.

That said, as long as the user is fully aware of what they are doing - I don't see any real difference between this and downloading the .stl file and sending it to a commercial print service.

maybe if the app gave you a wide choice of printing services and a small percentage of the cost went to the file designer - it would be better.