Ok, there's no doubt that GameMaker is one of the more popular game engines, especially for indie creators. I've seen a few MMOs and MMORPGs that have been made in GameMaker, but mostly just for fun and not as a serious project. I haven't really seen any games that are actually active and hold lots of people (I feel like those kinds of games are the best kinds of games). Is there any particular reason for that? Is there something about GameMaker that makes it unsuitable for (large) online games?