Load testing your applications is much like flossing your teeth or taking out
the garbage: you know you should do it; you know (vaguely, perhaps) that
there will be consequences if you don't do it - and yet somehow it always
seems to slip to the last item on the to-do list. Until, of course, there's a
crisis of some kind.
It's useful to reiterate why it's worthwhile to load-test before a crisis. In
the first place, you want to be able to give yourself and/or your client
confidence that the application you're building can handle the expected
traffic - and the only way to do that is to actually simulate that traffic.
It's a little too easy to assume that if an application performs well under
"normal" testing conditions that it will behave the same way (if only,
perhaps, a little slower) under higher-traffic conditions. In many cases,
however, that's just not so.