We already have self destructing notes (NIP-40 - Expiration Timestamp) but NOS Social is the only client (AFAIK) that uses it. 

We just need better support in apps. Would be cool to visualize them with some kind of icon/countdown as well.

One concern is that reposts (which copy the note's content) could be used to circumvent the expiration. 

CC  nostr:npub14vskcp90k6gwp6sxjs2jwwqpcmahg6wz3h5vzq0yn6crrsq0utts52axlt