wolfsite: True, Boycotts of this type rarely ever work.
When Steam first came out many wanted to boycott it due to the DRM and bandwidth usage at the time, however it became the biggest PC vendor and led to the fall of physical PC games. For a large amount of time it had a stranglehold monopoly and PC sales were more or less forced to use Steam as many people felt "No Steam = No Sale"
Many people have attempted a boycott of Activision/Blizzard but as we can see this has had minimal to no effect, (Hell Activision makes more money on Micro-transactions than actual game sales), they even tried to hold a protest at Blizzcon but very few people showed up and it barely got into the news.
However something to keep in mind is that if GOG did fall because of this, companies would say "See this is why DRM-free doesn't work" and then push DRM as vital for the industry.
Too true, Steam became popular only because it was the only way to get games, stores stopped selling them, Steam gained many exclusives... and if you bought HL2 in a store then all you got was a steam key. Hilariously, steam didn't do anything to stop piracy either, if anything it made it easier with stuff like pacSteam (allowed you to download any game without owning it, directly from steam servers.)
The problem is that there are far more gamers who are willing to cave than there are gamers who are willing to protest. It doesn't matter how bad DRM is for the industry, there are just too many people who cave and buy a game despite it having DRM. Microtransactions are insane, yet the only reason they still exist is because most people are willing to cave and buy games that have them. Even the lack of LAN multiplayer has to do with just how easy it became to leave it off without a serious dent in sales.
How can you fight evil when everyone else turns a blind eye to it?