It seems to me that return addresses are a weak point in vendor OPSEC. A buyer gives a screwy address and a pack of drugs gets returned to some stranger. Someone who recently got busted(RSS?) was using law firms as return addresses. While that's good from a package profiling standpoint, it's bad when it gets returned.
My suggestion is to use addresses of drug houses. In my city, in almost every neighborhood there are one or two run down houses with yards of trash, scuzzy people hanging around. If a pack of drugs got returned to these houses, it'll never be turned over to the police. I think there's a near zero chance that the police would be watching mail coming from these addresses. These aren't houses with internet access, many lack hot water and power.
Is this idea entirely crackpot?
A lot of people seem to think it looks more legitimate if the return address is a business of some sort.
I don't necessarily agree, but that seems to be the common line of thought.