It's not "me" thinking, there are several posts bringing this problem to the attention of admins, basically they took advantage of servers with open registration to "spam create" thousands of accounts, you don't see signs because they're "dormant" for now (that's what bots do when a spam campaign is not currently active), you can recognize it by confronting number of users with user activity, for example, if you see a server with 6k users and only 5-6 posts, it means it's a bot farm waiting for a spam campaign to start.