This is a tough topic for me; one that I see alot of BS on very frequently. I have personal experience with it. Not from a martial arts class, but rather from going to four different high schools. One of which had a grouping of large students of one race (20 or so) picking 1 smaller person of another race (in some cases me) to beat on for the sheer purpose of boosting their low self esteem or something..

So while alot of people spout theory freely, I have experience I can quote from. I would say the person I agree with anyone who said to run (look, it's not being cowardly - it's being smart), and with pretty much everything raspy said.

I have tremendous martial experience (12+ years, multiple arts) and had a fair amount back in high school as well (around 2 years) and found alot of things that did not work. Let me state a few:

8lbs of force does not break a knee, in fact, knees are pretty damn tough.
It's very hard to gouge someone's eyes when there's 20 of them.
Kicking someone in the balls usually does really work.
Biting is surprisingly effective.
Contrary to most training, people do not come at you 1 at a time.
You cannot always run.
You can, however, actually talk your way out of alot of these things.

In the end, there were only two physical altercations that I can remember. The first time I ended up on the ground, curled up, taking many shots.

The second time, I ended up on the ground, kicking and biting. After that, they never tried it again - I made sure the price wasn't worth the admission.

But in the end, I never had to deal with that partly due to a reputation (established at that point) and more in part to an enhanced ability to talk my way out of conflicts. It's amazing what you can convince people they don't want to do by being rational.

Nike-Fu is pretty good too. I was always a strong runner, so it was helpful at times.

Hrm... what else... Yeah. I would say run if you can, cover up your vitals (neck/head, stomach, jewels), fight back only if necessary.. and if you fight back make them earn it.

I've never found anything in training that closely resembles the madness of a 10-20 person on 1 'swooping' is. But if you can train REALISTICALLY for it, do it. Honestly though, Most formal training on this kind of thing will more likely than not hurt than help.

As for nowadays I carry myself in an aggressive posture, mind my environment, carry a knife (and am quite competent with it - 5 years of kali), and try to avoid potentially threatening situations.