May I ask a heretical question (especially from me):

 How many of you use call/cc and continuation objects
 (rather than mimicing continuations with lambda's)
 in large programs? Do "we" really use it to implement
 coroutines and backtracking and threads and whatever?

 Is call/cc necessary for Scheme?

[Don't shoot. I wrote many papers on all aspects of call/cc
but now that we're building large systems we should revisit
these questions. I'd love to be wrong here.]

-- Matthias