A question

What exactly is the purpose of this website?

It's just I've seen loads of people being tagged without so much as one link to evidence proving that they are in fact scammers.

Hell, someone got tagged over allegedly "stealing" a jpeg linked to him. Being a "furry" was thrown in there, too.

All I can draw from this is that the site only holds one purpose, public defamation of character.
How is that a "service" to the steam community at all?

I feel you are misinformed, but you seem like a very well spoken person so feel free to provide your steam information or add me yourself and Ill be more then happy to address in more detail with you, any concerns you may have.

We only mark per our guidelines, if any is wrongfully marked, they can appeal their tag.
The goal of this system is to protect other traders against and scammers, hijackers. Some sites also ban those that are "sharking" as a additional rule on it.

As such, we get regularly some heat or w/e. There was once a "competitor" but those didn't handle reports, or did any investigation. They listed a max of a couple dozen scammers, and stopped there.