"The big problem is...how can a protocol like this be made attractive to be used."
I don't know. How did the email protocol become attractive? However that happened, I'm sure glad it's a protocol rather than something that only AOL or Facebook users have.
If you post something on Facebook and tell me about it, I can't see it because I'm not on Facebook. But you can email it to me, and you don't have to say "You're not on Gmail, sorry," and I don't have to say "You're not on Fastmail, sorry."
Comments
Yes, maybe contacts should be a protocol.
"The big problem is...how can a protocol like this be made attractive to be used."
I don't know. How did the email protocol become attractive? However that happened, I'm sure glad it's a protocol rather than something that only AOL or Facebook users have.
If you post something on Facebook and tell me about it, I can't see it because I'm not on Facebook. But you can email it to me, and you don't have to say "You're not on Gmail, sorry," and I don't have to say "You're not on Fastmail, sorry."