I hate to burst your bubble, but the guy didn't regrow a severed finger, just a fingertip. He didn't lose any bone or the nail, just skin and a bit of flesh. And skin and flesh regrow. So there's no miraculous regrowth, just normal healing, so the most we could concllude is that it might promote or spped up normal healing.
Whats more, this is only ONE guys story, and there's been no published research on the pig powder. If this stuff even does so much as help skin regrow faster, why hasn't the researcher, Dr Stephen Badylak, published anything on it? A case study, a lab report, anything? He didn't even write up a case study on the guy who went to the newspaper about it.
Scientifically speaking, this incident is useless. It's not a part of any organized study, and even if it were, there's no point of comparison. Unless the guy had cut off a fingertip before, no one can even say if it healed any faster than it would have without the pig powder. That's why science works by performing experiments, studies, and trials; to establish for certain whether an effect is even occuring.
Dr Ben Goldacre has a nice post about this story:
Pixie Dust helps man grow new finger Bad Science
