In light of the recent court decision in Germany, which ruled that a person can be held liable for acting as a relay for copyright infringing data, the Relay option should be turned off by default.
Acting as a relay is an advanced feature, that will probably only be used by a small percentage of users. However, it can break the web of trust and allows a Retroshare client to unknowingly act as a relay for unknown persons, who only have to look up clients from bdboot.txt.
I think it would be the best to turn this feature off by default, with the default settings it's not really usable anyway (bandwidth).