jdMorgan - 3:19 pm on Mar 16, 2010 (gmt 0)
The [L] flag ends mod_rewrite processing if the rule is invoked.
Since it is unlikely that you would want your server to have to test all of the following rules after matching and invoking a particular rule, this is a question of efficiency. The best way to avoid prematurely-required server upgrades is to avoid wasting CPU cycles, so the [L] flag is almost always a good idea. By the time you need code that you wouldn't want to use the [L] flag on, you'll know why you don't want to use it, as it's generally only not wanted for certain "advanced" coding techniques.