status of shared or hybrid heap?

[tsuraan]

Erlang has support for -shared and -hybrid, which seem to be different
ways of not having processes have totally separate heaps.  Where can I
find documentation on these options?  Also, is there any plan for
making one of the heap sharing options default at any point?  I've run
into problems with blindly applying pmap with closures with large
amounts of data, and having my program run out of memory.  Shared
heaps would probably make this a lot less likely.