PSA (Joe Orlando / Steve Sloan): Either horribly incompetent at detecting alterations or partially incompetent and partially complicit in fraud, giving favored submitters higher grades than regular Joes or passing through altered cards as unaltered to keep the submissions rolling in.
BGS: Incompetent at detecting trimming on modern cards; have been giving favored submitters like Leaf and Joe Clemons (former BGS employee) an impossible number of BGS 10 (Pristines and Black Labels with all 4 BGS 10 subgrades). These sell for like 5x what a Gem Mint 9.5 card sells for on the same modern cards.
SGC: Graded some very high value trimmed or recolored cards with numbers at the National Convention (like $50K each) that were outed, plus were heavily used by OCSI to grade trimmed cards. Not used as often on modern since their resale value is much lower than PSA or BGS. Also closed their autograph authentication wing after they agreed with JSA that 12 Sharpie signed T206 cards were outed as counterfeits and slabbed them as Authentic. Those sold for thousands apiece.
As of now, not many internal whistleblowers, but many high submitters who attended the BGS or PSA annual meetings have been outed as card alterers.
Small Traditions is probably the biggest auctionhouse who have been outed as trimming the heck out of cards, but it's highly likely there are others. Paper trails are smaller with auctionhouses because of their secret consignors and kind of invisible employees.
PWCC (Brent Huigens) is well-known already.
COMC had some former employees accused of trimming and selling through COMC, and some of their largest sellers were outed as trimmers. COMC is trying to buy back the cards that have been outed and their owner Tim Getsch has promised to write some code to detect trimming on cards in their scans. Refunds are super slow going since they only have a small team working the refunds, and that same team is supposedly also working their rollout of eBay auctions.
Check the
www.sportscardradio.com site to see many of the accusers trimmers and other scammers currently operating in the hobby.