I see the stuff you described and I'm always so thankful that humanity finally has public, anonymous dumping grounds for the worst of our id. It's therapeutic and, I think, healthy.
 A weak citation is here (but I bet you could find plenty more where that came from): http://books.google.com/books?id=Pye5IkCFgRYC&pg=PA853...
 Unproductive in the sense that it isn't helping anybody. As is mentioned in the book excerpt I cited in , this isn't even "relaxing" people, except from exhaustion. It would be better if they were doing something which reduced their arousal.
It's just appeasing to some people to stop respecting rules and decorum for a minute. No higher meaning to it. There's some more serious stuff too, but honestly, when I want to read something intellectually stimulating, I don't go to 4chan /b/ or to the textbox where anonymous people write whatever.
EDIT upon looking more: I retract that. The companion cube song is oddly intact though.
Two full days (some 20 hours) scrolling north, leaving messages and drawings along the way. I have met other people in only one occasion, the rest of the time I was alone with the messages and drawings left by other adventurers.
Energy surges made their toll one time or two, but I still managed to get to x0y2000. I felt enlightened. It was the most spiritual thing I've ever experienced.
Its minimalist approach and absolute freedom makes it one of the best "games" I've played. I strongly recommend trying it at least once.
And if you ever scroll north in http://www.yourworldoftext.com/jp, look for the messages from The Bard ♫ ;)
Then once you have this huge wordsearch, you sell printed poster versions.
Some of the non-/b/ areas of 4chan are surprising. Look at /jp/: there are people programming games and animations, people translating visual novels from Japanese. They even spawned a group project to make a visual novel from scratch: http://katawa-shoujo.com/
I think anonymous forums can work as long they share a strong common interest.
The linked page goes to one particular world: msernst which allows you to enter coordinates to scroll to (as well as drop links to those coordinates).
Looks like you can create your own text world or explore others.
Can this be used for useful collaboration?
I also played tic-tac-toe for a while, which somehow became at least 3 player with someone playing z's as well as X and O.
Browser dependent post-modernity!
Why am I addicted?