If the laws are at all like alcohol regulation, you can bet your bottom dollar venues will eventually develop "smoking areas" to cash in. Think about the $$ involved AND the demand for patrons being able to legally smoke MJ at your favorite concert.
You gotta start slow with legalization, but that scenario seems inevitable and highly tempting
And we would be bitching about the prices like we do with beer! Ten bucks for a joint, they are robbing us!