I don't think its so much GOG recycling CD Keys as the clown that posted a torrent some time back that had over 100 legitimate CD Keys that people had erroneously stored in online file repositories attached to personal websites thinking that was a safe way to store something.
One thing I've wondered, now that the master server authentication is gone, wouldn't it be possible to install the GOG version with the generic keys and then replace those keys with your own made-up multiplayer keys?
This. I have yet to see a duplicate key from GoG. I have seen dozens of them from torrented sites. About 10 times a year I get some clueless torrenter posting on our forums asking why there's a password on their account when they've never played on the server. This is, of course, why we have passwording in addition to the cd key check. I tell them first come, first served, and explain that a GoG key is only 5-10 bucks depending on whether they have a sale going. Otherwise all the torrented keys would be sharing vaults, wallets, and so forth. In fact, we also get a few gripes a year by people wondering why their items are disappearing, or one of their toons was deleted. It's because they haven't yet passworded their account, and another torrenter was logged in as them, using their items and playing their characters.
Torrented keys are pretty easy to spot. When you do a SQL search for most keys, e.g., key XXXXXXXX:
SELECT * FROM pwdata WHERE val LIKE '%XXXXXXXX%';
you get one hit. On a torrented key, you'll get dozens, if you have a busy server. I think my record is something like 250 hits. More typical is 60-70 hits.
About the only potential point of confusion occurs if you have guilds, where some players share keys. There, though, there's still a marked difference in quantity, with maybe 12-20 hits on a guild-shared key.
We do warn our players who share keys that it makes it difficult to distinguish them as different from those they share keys with, and that they may wind up responsible for that person's actions when using their key, but it hasn't been a major issue thus far.
Long story short...passwording. I think I've posted a passwording system, courtesy of acaos, somewhere on here. LMK if you can't find it and I'll repost.
Funky