Then you have the problem of "wait, which site did I sign up for this random forum for, google, facebook, or twitter?" and still keeps the problem of needing to

Then you have the problem of "wait, which site did I sign up for this random forum for, google, facebook, or twitter?" and still keeps the problem of needing to establish the account, things like a profile picture, signature, email preferences, learning that forum's etiquette, the forum's organization (where's "general"?), and then only after a non-trivial investment might you find out that the mods are actually dicks so it's not worth the effort. On reddit, I can click the "random" button and immediately discover a community that I can already post in. Do I want to talk on r/entrepreneur, or r/galaxytab (the actual two first subreddits that "random" took me to just now)? I can do that right now, and while there I also see the orangered envelope telling me I got replies to comments I made on r/zelda (also a true story of what happened when I just clicked "random").