This a double-edged sword IMO. I think it will be good for crypto as a whole due to the publicity, but it's bad in a sense that it'll be somewhat centralised being that it's run by facebook. I imagine it will fairly stable, as others have suggested, as you'll probably purchase it directly through FIAT, I guess? In theory I don't see any reason to buy and hold, or as an investment, it'll just essentially be like a global currency...therefore, it won't be as easily manipulated and fluctuating.

I think that perhaps short-term = good, medium to long-term = not so good.