The thing that bugs me is that you could have good password practices. But if you're having a party, having a fun time (and lets face it, people are going to do shit...), and one of your friends is snapping photos of you, and they have bad password practices, then you are kind of screwed. People don't typically make friends on the basis of: do you have good password practices.
Information my friends have is something I've had to accept letting go.
I once resisted signing up to Viber because it required that I upload my entire address book. However, I found out how many of my friends are already on Viber, which means the likelihood that Viber didn't already have someone's contact information was very low. It also meant Viber already had all of my contact information.
Another scenario is Facebook's tagging. Even if I don't confirm all (or any) of my friends' tags on my face, the fact that they manually tagged the face as mine likely counts a lot for FB, so that battle is already lost.
OTOH, if you're a celebrity at a party, and you "do shit" and someone takes a picture of it, the horse has pretty much already left the barn as to whether that picture is going to show up on reddit and it's just a question of when...
Yup. And that very reason is why many people don't have social networking accounts. You can control what you share, but you can't control what your friends share.
How not having a social networking account helps with that? Not only you still can't control what your friends (that is, the real-life ones) share, now you're the last to know if they share something about you.
Perfect example is Facebook. You don't have to be on it for them to know your phone number. If 2 of your friends have the "Share your Contacts with Facebook" option turned on, chances are Facebook has your phone number/whatever else your friends store on their friend about you.
Or: you've got good password practices, but you send content to someone who doesn't. Or they do. Or their friends do ...
When you realize that celebrity nudes are only the tip ("just the tip") of this iceberg, the real implications start sinking in.
The groups trading in info were also targeting exes and other associates, possibly businesspeople, politicians, and others, and the information in question isn't merely skin pics but _anything_ that was on those accounts.
Or you can use two-factor and strong passwords everywhere, but if your spouse is still using "letmein" on every account, you're gonna have a bad day soon.
