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They're a great fit in many situations but certainly not all. Why not teach programmers a variety of allocation strategies and how to recognize when each might be a good fit?

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I initially read your username as boehm, and I was like wow, ok, this is a guy who knows his memory. :)

What situations would an arena allocator prove problematic or non-optimal, aside from the many allocations/deallocations scenario?

This is an area I'm very interested in, so any info would be appreciated.

In general, everything allocated within an arena has its lifetime tied to that arena. In lots of situations this is a fine or even desirable property (e.g., a single request context in a server application), but can be a tough restriction to work with in situations where you need fine-grained deallocations and possibly want to reuse freed space. The lifetime property can also be a pain to work with in multithreaded scenarios, where you might have multiple threads needing to access data stored in a single arena. Another situation that comes to mind is large long-lived allocations where you might want to have some manual defragmentation in place for performance reasons.

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