Unofficial (Bootleg) LPs

As you know, Discogs now blocks any listing that shows "unofficial" as label/source. My suspicion is that neither E Bay nor Amazon block such offerings unless they receive a notice, similar to a take-down notice, from a party in interest (e.g., sound recording rights owner).
A couple years ago I was on the phone with someone at Universal who was combing through their archives for me, using Discogs to check some information. In a couple cases (this was before that platform instituted a blanket ban on "unofficial’ releases), he saw a few for the masters we were researching that were not licensed and he said "I’ll have to let Business Affairs know about these."
There are several questionable labels still on sold on Discogs that are known to be "iffy" as to provenance, yet still appear today for sale. As to "legitimate" sellers, pretty much anybody can be a (re)seller, often with a high feedback count, from their home, basement, whatever.
From the sound recording owner’s perspective, it’s a question of time and resources to play whack a mole. My experience in the old days with record piracy or bootlegs is that the major labels went after the bigger plants if they could identify the source; it didn’t pay to chase downstream sellers for many reasons other than a letter the equivalent of a takedown notice to an Internet platform. The selling platforms didn’t and probably still don’t research the legitimacy of the label, and weren’t/aren’t incentivized to do much on their own to stop this. Suing for Amazon or E-Bay would not be the first step in most cases. In the good old days, a record retailer typically wasn’t sued for piracy unless they were more directly implicated in the actual manufacture of the records, even though distribution, without more, is actionable at least in the States as copyright infringement. The DMCA notice and takedown provisions have also probably had an impact on approach (even though I don’t think they literally apply in these instances to provide a safe harbor), in addition to cost effectiveness and resources from the perspective of the rights owner. No legal advice intended or supplied.

@whart 
Nicely stated whart.  
My main frustration is buying a release that looks 100% official from a reputable dealer, only to discover that it is a counterfeit.  
It's pretty easy to spot bootlegs, as they are usually live recordings, most of which have circulated in tape trading circles for decades.
An example is Grateful Dead's Cornell show.  Before the official release of this show on vinyl, you could only get the inferior sounding bootleg.  
The packaging and graphics of bootlegs are typically not as sophisticated as official releases, making them pretty easy to spot. 
I never buy bootlegs these days but in the past, when it was difficult to find them (pre-internet) I coveted them, so I am not against them.  I just want to know that what I'm buying is officially released by the artist/label in making buying decisions.  There are also some famous jazz titles I have bought on vinyl and later discovered they were unauthorized versions pressed overseas.  Simply Vinyl is a label that has pressed a number of famous rock titles that look identical to the originals, all sourced from CD.  I view these labels as rip-offs that are very hard to discern from the real thing.  Vinyl collecting requires more diligence in researching before buying, and unfortunately many online sellers provide less than thorough info on specific releases.  Sometimes it's a crap shoot.   

I love old bootlegs. I had a nice collection of vinyl bootlegs from the late 70's and early 80's. It was the epitome of cool to play U2, Stones, and even the Grateful Dead bootlegs in college. While the worst editions had horrendous sound quality, the best examples captured the intensity of the live shows from their respective bands. I appreciate the financial consequences for labels and the artists themselves, but realistically the bootlegs represented the ultimate fan appreciation- people willing to pay a premium for new work by their favorite artists. The Dead figured that out a long time ago. I am not talking about fake Chinese copies of official releases. I bought a counterfeit Beatles box set off of Ebay a few years ago. The quality of the copies is amazing. However, close scrutiny of the "Revolver" album revealed spelling errors like George Harrisun, etc. I have purchased some cd bootlegs off of Ebay recently. Most of them are old radio broadcasts. The quality varies, but some are fantastic. My favorite is a 3 disc set by Joe Walsh of live recordings from the 80's and 90's. I think people forget what a fine slide guitar player Walsh is. These bootlegs inspired me to purchase his more recent solo releases. I had not thought of Walsh in years.