I can't say with certainty how it is for raves, but i know that with a lot of the clubs i go to, nobody has ever questioned it. Maybe security is tighter at raves, but i've never had more than a quick pat down done before i went out clubbing. And i wouldn't worry too much about needing to change, i usually only go out with a clutch or something small, so there's not much room for a backup diaper. I guess it comes down to how much you drink (and what you're drinking), and how small your bladder is. But i wouldn't worry about security. Believe it or not, some people are incontinent in everyday life lol, you definitely wouldn't be the first person they've seen wearing.