guidelines for refcounting / cbdata

Do these seem right?

*) Use cbdata for any asynchronous calls, where the caller may disappear
during the calls duration. I.e. calling a acl checklist from a http
request object. An alternative but more complex approach is to have
'backwards facing' refcounting, where the callee holds a reference to
the caller. Such a design needs more thought than cbdata, and cbdata is
advised unless it is insufficient for the needed behaviour.
*) Use refcounting where multiple objects may use a single object, and
no 'last user' can be guaranteed. I.e. refering to a specific acl entry
from a checklist.
*) Use both if needed following the programmer guide howto. I.e. a
shared resource (say store entry) that may pass itself to a async
callback object.

Rob

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