Social Media accounts with private DMs are the first to pop in mind. Cloud storage like Dropbox/iCloud/Drive/etc. Lots of things really if you thing on it for just a minute or so
If someone DM'd me, they were probably expecting me to not share what they said. If I have stuff in cloud storage that could be useful to others, I'll share it now.
I'm sure there are use cases, but it's actually very hard for me to think of them, let alone in just a minute or so.