My pools are named "pool1", "pool2", "pool3" in all my installs. You don't need a default pool, either (you do with ACS Classic 4.x, though).
If you define a list of named "availpool"s it will only use those, very useful if you're talking to another database (migrating from 3.x to 4.x, for instance, or talking to a non-ACS database containing stuff you need).
Thus far I haven't seen any instance of needing more than three pools.
