when you're jogging, your back carries about five times your body weight.
this, however, is completely normal and actually strengthens your back. It's another common misconception that swimming is good for your back- but actually, you bend your spine (your neck) unnaturally while swimming, plus your weight is being carried by the water hence not enough back muscle exercise, so it's a double no no. Unless, I guess, you're already so crippled that it's the only exercise you can get. Otherwise keep running and exercising. I will admit doing the back exercise thingie at the gym (I forget the name of it, but it's the opposite of the ab curl, ie your'e pushing back) scared the shit out of me the first time I did it, because I got a muscle ache in my lower back. But, that's a good thing!
the other problem is that once you classify yourself as always having these back pains all the time, you start actually avoiding the sorts of exercises that would HELP you, and people even get nervous and thus tense their muscles and try to move in a stiff way and ta da, more back pain. It's such a horrible cycle.
I don't know about snowboarding though. I don't see why it would be explicitly bad for your back.. but I guess it'd be easier to hurt/strain yourself than with jogging. I bet the pressures on your back would be more than when running, too. But look at other sports.. like tennis. that twisting motion is pure torture for the spine. But how many professional tennis players have back problems? I'm actually asking 'cos I don't know but if you look at professional snowboarders and see what their typical ailments are, you'd probably get your answer.

ok, that was the last edit, I promise.

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