Phone notification: "HELLO, THIS IS THE OMNISCIENT COMPUTER NETWORK 'FACEBOOK' AGAIN. MOMENTS AGO, A MALE COMPANION PROPOSED A LIFETIME OF WEDDED BLISS TO YOUR FORMER GIRLFRIEND. SHE SAID YES. ATTACHED IS A PHOTO SHE SELECTED OF BOTH OF THEM LOOKING ATTRACTIVE."
> Except before Facebook, we wouldn't have known this unless we went out of our way to find out, or just ran into our ex in the street.
Or had any common acquaintances. Or read newspapers (publishing engagement notices in them used to be a thing).
For most of human history, if someone you used to be involved with was engaged to be married, it wasn't particularly unlikely that you'd hear about it, and in many cases be either socially expected to participate in celebration related to it or be pointedly excluded from them.
In fairness, for things like "engaged" or "married" Facebook promotes the heck out of those events making them very much a "big event you should be excited about".
If you're a decent human being, you should be happy for a past partner celebrating an important moment in their life. If they're happy, would you not be happy for them?
Phone notification: "HELLO, THIS IS THE OMNISCIENT COMPUTER NETWORK 'FACEBOOK' AGAIN. MOMENTS AGO, A MALE COMPANION PROPOSED A LIFETIME OF WEDDED BLISS TO YOUR FORMER GIRLFRIEND. SHE SAID YES. ATTACHED IS A PHOTO SHE SELECTED OF BOTH OF THEM LOOKING ATTRACTIVE."