I'm almost certainly drifting this off-topic, so moderators step in if necessary, but since Frank asked...

What are scoped allocators useful for? This has bothered me for a while. I've read [1] and it's not really motivating me. What's the problem with just feeding the right allocator to the right object when that object gets constructed? Why should containers be complicated by concerning themselves with what allocator their elements use? Couldn't that be left to the client of the container?

[1]  http://www2.research.att.com/~bs/C++0xFAQ.html#scoped-allocator