One big problem with pools is that you have to deallocate the pool sometime (or else your program's working set will continually grow over time), and when you do, all the pointers into that pool become dangling.

Another problem with pools is that you can't deallocate individual objects inside a pool. This is bad for long-lived, highly mutable data stores (think constantly mutating DOMs, in which objects appear and disappear all the time, or what have you).