It is proven to be broken down into carcinogenic metabolites in rats, but that hasn't been proven in humans.
I'm not saying for sure that it isn't carcinogenic, but then oxygen is quite highly carcinogenic, and I wouldn't recommend against continuing to use that everyday. If it weren't for MDMA I think that more research would be done on it, to clear-up the question of carcinogenic status once and for all. As it is I suspect that the increased risk of cancer is likely to be low.
http://www.aromaconnection.org/2009/09/safrole-human-carcinogenicity-risk-over-stated.html
I'm not advocating ignoring warning signs and using the stuff, just trying to give a measure of the real level of risk that you would expose yourself to if you did.
Safrole is not used much in fragrances because of its links to cancer, no other reason. Safrole can actually be easily obtained from sources other than sassfrass root bark. There is a certain type of S american houseplant which, when steam distilled, gives 70-90% safrole. If demand was increased, then this could turn into a sizeable cash crop for Brazil the surrounding countries, because the oil is obtained from the whole plant rather than just the root bark. The plant also grows vigorously.
