There is an article devoted to continuation-based web servers at IBM developerWork.
I'm pretty sure that this technology will eventually become mainstream, like many other technologies first introduced by the Lisp and Smalltalk communities. Remember that Christian Queinnec was probably the first to use continuations for web programming in Scheme (proceedings of ICFP'2000). He was then followed by the PLT-Scheme guys, the Cocoon project (JavaScript), Avi Bryant's Seaside (Smalltalk), and many more. Even Paul Graham used similar ideas in ViaWeb - now Yahoo Store! (in fact, he used continuation-passing style instead of true continuations since the latter are not available in CommonLisp).
The article got a lot of attention on Lambda the Ultimate, Planet Lisp (via Bill Clementson), and Planet Smalltalk (via James Robertson).
