Andris Birkmanis posted a reference to a paper, by David Teller, on resource recovery in pi-calculus on LtU. I'd not really thought of dead process collection in terms of garbage collection before, but it certainly makes sense when thought about.
This is also something to think about with the growing interest/importance of modal web applications (continuation based a la Wee, Seaside, RIFE, Cocooon Flow) which effectively model a session as a continuable process. I'm wandering away from David's paper, but how to handle the growing memory requirements of a bunch of continuations in the session gets hairy. Cocoon does it, thinking in terms of GC, via explicit "memory" management, where continuations are stored in a tree structure and you are responsible for invalidating them yourself. Not sure if there is an equivalent for "dead back button detection" as there is for dead process detection.
Ah well, food for thought after I've had some more coffee.