On 28/05/07, Mark Ruzon
I would hope that no one who writes useful algorithms tries to prohibit reasonable actions from taking place just because they're expensive. It is not up to library designers to save programmers from themselves; programmers can always write inefficient code if they choose not to think carefully about what they're doing. This is one of the founding principles of the Standard Template Library, and one that should continue to guide Boost.
From what he said earlier, it appears Thorsten Ottosen now agrees: "In 1.35 I plan to change this so all ptr containers can be copied. I still don't recommend vector< ptr_vector<T> >, but I'll let the user decide when he wants to copy."
I suppose it's also plausible that SFINAE problems in compilers that will no longer be supported in 1.35 were partly to blame.