In larger, more serious races, if somebody fouls you and you do not protest, and if another competitor observes the infraction, that other competitor can protest you, in turn, for not protesting.
Mary,
I'm not aware of any requirement to protest. The closest thing I see is the preamble to the rules which says competitors are expected to follow and enforce the rules (an expection, not a requirement). Under what rule could someone protest you for not protesting another boat? In other words, what rule do you break by not protesting?
I know you don't have to be affected by a Part 2 infraction to protest (you only have to witness it), but I don't see any rule that says you must protest.
Regards,
Eric