With amount of people who actually grow now-a-days you can usually get cannabis from a well known source who you can trust. It hardly gets smuggled in and cut with other drugs and redistributed anymore. Atleast not where i'm from. I know many people who grow indoors and some who grow in the nearby mountains. They are all friends of mine and i know they don't add anything. So i guess it all depends on where you get it from. But hey if it was legal and monitored how it is made then i guess you could trust it more then?