Hi Consider this example of mem_fn usage: struct X { int bar; }; std::vector<X> vec; .... boost::make_transform_iterator(vec.begin(), boost::mem_fn(&X::bar)); The above is, strictly speaking, _not_ a Random Access Traversal Iterator, or even a Forward Traversal Iterator, and would fail in otherwise concept conforming code (or in a potential concept-check). The problems lies in the function objects returned by boost::mem_fn and boost::bind not being default constructible, thus making the resulting iterator not default constructible which is required by the Forward Traversal concept. http://boost.org/libs/iterator/doc/new-iter-concepts.html#forward-traversal-... (The problem is even more pronounced if using the "old" Iterator Concepts.) I found an old (2002) mail by David Abrahams where he also noted the problem: http://lists.boost.org/MailArchives/boost/msg30420.php But it didn't seem to have resulted in any change of the codebase. I think use-cases similar to the one above are good motivation and hope this could be considered an acceptable improvement. Regards // Fredrik Blomqvist P.S. I realize it is very close to the branch for release and don't expect this to be added before that.