Most people I sail with have no idea what their rating means or how the system works. Consequently, they report their numbers wrong (or not at all) during registration and expect the RC to figure it out.
I agree Jerome. . . but then there are those few sailors who know exactly what their number is to their modified boat, and intentionally provided a slower number. There are a few at every fun regatta. They get away with it. They get away with it time and time again 'cause they know they can and the host strongly discourages protests. They know it is wrong but still do it. Why have handicap racing if you don't enforce the rules? Someone ALWAYS gets screwed unjustly. It is only my opinion, but the open class handicap racing (Portsmouth corrected) model is broken, and for more than a few reasons.
Sorry for the rant, I'll get off my soapbox.