why isn't there a feature to recognize or mark a model that is shared from another site?
It just isnt fair the idea is to share your models maybe even your work, but theres quite a few who take models from other sites and upload them, then get credit for that, or a great position in the rank,
I also think there should be something done for the ones who upload each individual part of an assembly as a different model, hence getting lots of uploaded models at the cost of flooding the library with useless files because most of those parts are useless out of their assembly.. Hope there's a few who agree with me...
6 Answers

J.E - we completely agree and support your opinion regarding taking models from other sites and uploading them as your own without reference to the source. We all take integrity seriously and if there are users mass uploading models that are simply downloaded from some place else without reference, we have taken action in such cases.
What you (and everyone else) can do is simply pay attention to this questionable activity in the comments of the file. If the engineer still takes credit for something (s)he does not deserve, then you can always contact GrabCAD staff and we'll be in touch with the user directly.
There will be changes in the ranking algorithm as the GrabCAD platform develops and gets more sophisticated and engineer-focused. The CAD files component will remain (as it does reflect how active the user is and that there are examples of his skills and work), but likely from a slightly different angle.

I agree.
But it is very difficult to separate this kind of thing.
I think users should vote, and votes anonymous "disliked" in the drawings would be a great option?

I agree, but ... the person who uploads models taken from other sites without giving credit won't care to use this mark ...
From what I've seen, a lot of these sites are making their living from these models and uploading them here hurts them financially ... even if these particular models were offered for free on these sites ...
If someone liked a model from another site and wanted to share, the proper way to do it is post a link and not uploading it here. I think Scott Bruins sets a good example here ...
And yes, posting each part of the assembly is somehow troublesome for either people who want to download or the ones who are just browsing, giving that these parts aren't useful without the rest of the assembly, I don't think much of the ranking though ...
Finally, it works the other way around, some people collect models from here and mass upload them somewhere else, you can't really do anything about it ...