As with any form of exercise there can be damage done it it's done incorrectly or overdone.
I tried it out of curiosity and it did me no harm. I don't think anything bigger than 7 inch is necessary though, but I do feel sorry for those guys who for whatever reason, poor diet, genetics, etc, do have a small member. Especially in this day when emphasis is on bIG.
I also feel sorry for those girls who feel the need to get breast enlargements who really don't need them. Very few girls/women need enhancement. It's just a sign o the time, how superficial we're all becoming.