The second instance being, when the sack is generally embraced for one reason or another. This can happen again during oral, the significant other cradles the sack in hand, or this could happen in any rare male bonding situation, involving the sack being embraced for no reason.
The third possible instance being a situation where you would refer to someone as a cocksucker... instead, refer to someone as a yam bagger, its funny, interesting, and the person will spend some time thinking about it before responding.
I went to tea-bag jimmy while i was wearing short-shorts the other day... not good... he ended up bagging my yams! When you see him, call him a Yam Bagger.
You dirty little yam-bagger!
During the induction ceremony for the fraternity the head hazer bagged my yams... i think he liked it; Yam Bagger...
You bumped into me! Watch where your going yam bagger!
You sir are a yam bagger!