I have to agree with Hagane on the grappling with multiple opponents aspect; the last thing you want to do is end up on the ground. BJJ may have ways to adapt and cope with many assailants, but let's be honest here. The main strength of BJJ is the grappling. If you have to deal with more than one attacker, rather than sticking to the striking elements of a grappling art, you'd be better served switching to a style better equipped to handle feet-on-the-ground fighting.
Of course, I think it's important to distinguish learning a martial art to learn a martial art (and any philosophical/spiritual/noncombatative elements that go with that), and learning practical, street self defense.
For example, maybe I want to learn Wushu or Aikido. If someone tries to mug me on the street, I'm sure as hell not going to try and use Aikido unless I've had thirty-odd years of constant practice and experience with it. I'm probably not going to use Wushu either, since the risk of pulling off all the acrobatics without proper stretching could be problematic (unless I happen to be in kickass shape).
That said, lets endeavor to distinguish when someone's talking about aesthetics and principles of a particular art, practical self-defense, or just making a joke.