It has the added benefit of potentially being a real-time conversation as well--this sometimes happens with a flurry of short emails, but it's much more awkward.
I was hoping Google Wave would take off an neatly combine the two. But it never did :(.
This is the best thing about Facebook messages: they’re hafway between chat and email and a conversation can seamlessly morph from one form to the other and back.
- You can't read them without announcing that you did.
- FB parses and might even censor you message if it contains blacklisted domains.
(The obnoxious thing is that both of our phones are Verizon iPhones; there's no simultaneous voice and data, and unlike me, she tends to do long voice calls with people. I'm trying to get her to switch to a SIP client, so we can do G.722 wideband and crypto/vpn on the voice too, and non-extortionate international long distance.)
I don't know about the site itself, I really only interact via my phone.
It's been around long enough now that you probably don't have to worry about it going away anytime soon, and its users really like it.
(I am not affiliated)