Perhaps a thread with a list of vendors who have been "proven" to have problems. If a vendor is posted in the thread, the proof should be posted in the form of hyperlinks to the relevant posts/threads substantiating/documenting such behavior.
The thread shouldn't be used to investigate or build a case against a vendor. It should be used only if the case has been conclusively made elsewhere.
Also, I personally find the word "scammer" overused. The criteria can range from a source who takes money and sends nothing in return to one who sells counterfeits to one who sells overpriced gear ; one who sells bunk gear to one who sells contaminated gear to one who sells underdosed; one who has inconsistent customer service to to one who has terrible customer service to one who makes death threats against members.
The qualitative distinctions may be important when discussing an androgen black market where practically all vendors meet one of the aforementioned "scammer" criteria.
This qualitative data would be of considerable value in such a scammer and/or sources-with-problems thread.