I never did, because there was a lot to lose and nothing to gain. But each situation is different.
I would recommend you know the situation and try to gauge how well they will take it. If they are more liberal people, they might be more likely to accept it than someone who is more conservative.
If you figure you can tell them, tell them in an adult manner, not just going up to them with a wet diaper and showing them. Do your research, find good sites and info about this before saying anything, so that you have something to fall back on.
Also, I would recommend that you are honest about your diaper beginnings. I would have had to tell my mom she is the one that planted it in my head, because she constantly threatened to punish me with diapers until I was 16. This probably would have went over rather badly.
But everyoen has their circumstances in life that they need to figure out. Figure out if there is an inherant need to tell anybody, and if they need to know, figure out how you will tell them without totally putting them off or creeping them out.