I feel like the key word for this thread is recklessly. I use buying groups and though I would hate to take a total haircut the max I've ever been owed in total was apx 30k. A loss like that would suck but I've paid back more than that in student loans so I know I can dig myself out of that hole and a it wouldn't wreck me. But a 200-300k loss, that would wreck most anyone's finances. It's basically like having your home burn down and you are uninsured.
I think that the BG's and other shtick can be a great way to get extra cash to sock away. Personally I try to max out my Roth IRA's with the extra "income" so I never end up relying on it. That's really a big sticking point in this game. So many people end up relying on the point revenue that once a stream dries they have all sorts of nasty things to say instead of being grateful that they fell into such an easy revenue stream in the first place.
But as many have said there's risk involved. It's very hard to know your risk tolerance. I work for a large fund company and I overhear CSR talking with clients about their risk tolerance on a scale of 1-10. It's laughable when you hear, um I think 8? If you think your risk tolerance is an 8 you should expect to have 50%+ drawdowns perhaps 2-4 times in a 50 year investment plan. If you want to think about risk tolerance 30k = crashing an uninsured brand new car into a brick wall for a total loss. 200-300k = burning down your house without insurance. If you really think about how you would feel if either happened to you, you'd start to have a clearer idea of what your risk tolerance is.