It would be convenient if the visibility settings on a swarm allowed you to share the swarm with only your untrusted friends, or the whole network as if all your friends were untrusted.
Example: Lets suppose I join a music sharing private community server. I rip a rap CD that I wish to share with the community. Unfortunately, the majority of my friends hate rap music and do not know I listen to it, and I wish for it to remain that way. Currently, the only way of sharing the file with my untrusted community contacts is via the "All Friends" visibility option, which allows my rap-hating friends to see that I have it.
In the above scenario, the problem could be avoided by sharing the file with only trusted friends who lack any particular rap prejudice, but at the expense of (perhaps greatly) increasing the number of nodes the traffic has to pass through before reaching the intended destination. It would be far easier if I could simply share it with a selected group of community contacts directly, or if there was an alternative to the "All Friends" option which treated all friends as being untrusted.