This isn't the end to Facebook's plans, either. The company is planning more unsend features that might include setting expiration dates for unencrypted messages or entire conversation threads. You might not have to keep an outdated party planning chat in your conversation list, and you could automatically purge your backlogs if you're worried about someone peeking at your old discussions.

There are potential cynical reasons for adding an unsend option. It could help execs keep conversations secret (Mark Zuckerberg learned this when 2004 chats leaked out), and might reduce liability -- investigators can't read messages that don't exist. Even so, it's a helpful nod to user control over data from a company that is still learning what its users really want.