Getting arrested for marijuana is no joke. Marijuana arrests result in fines, and can result in jail time, loss of driving privileges, loss of college financial aid, forfeiture of assets, and many other penalties. I've only been caught with marijuana one time (half ounce, 2005), but since I live in Oregon where marijuana is decriminalized I only had to pay a fine ($500). I didn't even have to go to a courtroom. I just had to go to the window at the Clackamas County Courthouse and pay my money.
Obviously had I been caught with a half ounce in Colorado or Washington today, there would be no penalty. I hope Oregon joins those states soon. Other places are not as friendly as Colorado or Washington. In some states you could be looking at serious time for just a dime bag. My cousin in Idaho got caught with a used marijuana pipe and had to serve six months in jail for.
Where in the United States are you most likely to get arrested for marijuana? According to an ACLU report from earlier this year, Washington D.C. had the highest rate of marijuana arrests. The report calculated for population size, so this is not the total amount of marijuana arrests in an area, it's the highest rate of marijuana arrests per 100,000 citizens. New York State was second, Nebraska was third, Maryland was fourth, and Illinois ranked fifth.
In Washington D.C. if you get caught with any amount of marijuana, even less than one gram, the penalty is six months in jail and a $1,000 fine. That's a brutal penalty for something as harmless as possessing a dime sack of marijuana. If you live in Washington D.C. and you consume marijuana, watch out. Obviously you want to proceed with caution no matter where you live outside of Washington State and Colorado, but be extra careful if you live in D.C.
The state that you are least likely to get arrested for marijuana? Massachusetts. Keep in mind, this study looked at the most recent numbers available, which was 2010. I'd expect Washington and Colorado to drop on the list considerably once 2013 numbers become available. No one should ever be penalized for marijuana. Do your part, contact your legislators, and fight for reform any chance you get!