Many people in all sorts of content have that content as a sideline and can therefore afford to give things away for promotional purposes.
Also, in Second Life, I'm sure we'll be seeing lots of people putting up cheap videogame ripped meshes.
Well, the exporter is supposed to take care of that, but the fewer steps you leave to the exporter the more that narrows it down.
Maybe try exporting a single link and see if it still hangs up on import?
Are all the faces triangles? Are there any modifiers that might have caused a problem with the export of the model? Does the DAE file load back into Blender properly?
I don't read German, but it seems you have the option to include joint positions checked; in that case, if the imported model doesn't have bones all weighted segments will be centered on the origin.
It would be nice if you could overlay a lightmap/occlusion texture over a tiled texture. That way you could get away with a much less detailed baked texture since the tiled texture would handle the details.