4chan has no economy of scale in the UI (i.e., reddit gets more interesting with more posters but imageboards get less interesting), and has no signup barriers to stop new users. The veneer of rudeness is intentional and acts to maintain quality, not reduce it.
Also there are many active topical boards like /an/ /cgl/ /fit/ /u/ you're not reading!
I thought 4chan was the largest forum on the Internet, and in fact I remember when 4chan displayed the total amount of live content on their servers as being 100GB. Now it's more than 1300GB. 4chan thus seems to have become more popular.
People really do hang out on 4chan, though it's lost some share recently to 8chan, but 4chan is certainly a very large forum, the 200k+ current users, as displayed on their homepage too, confirms this.
For a place where you don't have to worry about drive-by downvoters, for all its faults, 4chan is excellent for getting your opinion across.
I meant compared to the really large scale social networks.
I don't know how accurate this is, but to put some numbers on it, Reddit seems to be #9 and Twitter #11 according to Alexa [1] and 4chan is rated much lower [2].
Although, Hacker News ranks higher than I expected [3], which seems suspicious. Perhaps there's a better way to measure it?
There's a chance HN could be artificially compressing the number of upvotes site-wide in order to maintain the illusion of smallness. Reddit did this same thing for nearly a decade.
E.g. Obama's AMA only appeared to have 14k upvotes even though in reality hundreds of thousands of people voted on it.
It'd be harder to get away with on HN, but maintaining the illusion of a tight-knit community for as long as possible is pretty crucial to the site's success.
4chan makes almost $0, for all the time moot poured into it and all its supposed users. Moderation or lack thereof is probably why the ad space is so worthless. Its silly to compare it to Facebook.
Also there are many active topical boards like /an/ /cgl/ /fit/ /u/ you're not reading!