Having read through this thread, I'm very relieved that I never had any naughty photos of previous girlfriends (and, indeed, that they didn't have any of me!). There are some difficult issues here, and I'm unable to provide clear-cut answers to the questions.
Generally, I'm a bit of a hoarder, so I probably wouldn't have thrown away any moderate photos. I still have some decent (fully clothed!) photos that feature early dates and bring back happy memories. If I had any naughty photos, though, then I'd have probably got rid of them because they'd probably be painful for me to review and they could also be a hostage to fortune.
One thing that I can't imagine myself doing, though, is to show around or publish any naughty photos of a current or previous partner without explicit agreement. I think that my friends (at least) would be extremely unimpressed if I tried to show off in this way, and I think they'd have good moral grounds for telling the partner what I'd done.