How long should social media posts be retained? That's an interesting question.

Facebook, for example, retains everything forever, not just posts, but also searches and private messages. Some newer social media protocols are based on an append-only log (which means old posts can never be deleted).

But much we say on-line -- not all -- is really similar to a conversation with friends over a beer, and we'd be appalled if we'd record each other then and keep for years.

What's best?