Per Evan Prodromou’s request I shared a tiny bit of my knowledge at WikiTravel:Austin. Because I could do so without asking permission, I also copied some text between WikiTravel:Austin and World66:Austin. Due to both having wisely chosen to use the Creative Commons Attribution-ShareAlike License, WikiTravel and World66 each now have slightly more and better information about Austin, Texas.
WikiTravel benefitted slightly more from the exchange, as it is easier to add useful content to. World66 content is split into more individual pages, requiring multiple page edits where a single operation suffices for adding the same content to WikiTravel. At some point a page does get too long, but my preference is for much longer pages than most sites present — less clicking, more effective in-page searching, and less of a pain to print. More importantly World66 segregates links to external sites from other content. C’mon, this is the web!