I'll admit that I don't go around looking at other RPs very much. But some of the best writing I've ever seen in an RP came from a collab. I have yet to see a [i]really[/i] bad collab post. I have yet to see one that limits interaction. There's almost always some form of plot advancement, be it characters becoming closer/further apart or some type of reveal. 

Do they always involve the other characters? No, but very few solo posts do this either. In my ten plus years of collaborative writing (most of which was not here), I have seen very few bad collaborations. The ones that were bad usually took too long to write and were no longer relevant, or the characters didn't really have anything worthwhile to discuss. The problem was never the collab, but the planning of its execution. 

Collabs are definitely a tricky subject, one that probably deserves its own topic. My goal here was just to take collabs back to basics. They are a tool. Not a cure all, but certainly not a poison. 

...now I want to make a guide for the site on how to properly collab.