Interesting, why there is still no chat-on-blockchain thing. Sounds like an obvious idea for an ICO.
What would be the point anyway? A dedicated peer-to-peer messaging network that doesn't need to keep track of the entire history of everything seems much more appropriate. IRC comes close to that with its federated architecture, although I suppose a completely seemless bittorent-like peer-to-peer chat using public key cryptography for message authentication could be pretty great.
Chat on IPFS is a good idea, though.
Because in engineering, the question is not "why not", but "why". Blockchains are not the default answer. What positive virtue is blockchain going to bring to your IM system that is not better attained by a non-blockchain-based solution?
If you can answer that, great. I'm not saying this has no answer. I'm just saying it's the real question.
If you are going to say the word "federated", then from what I can see, trying to do "blockchain" at that point isn't all that helpful and likely to be worse and harder than just trying to develop a federated system, a sufficient challenge on its own that doesn't strike me as greatly helped by "blockchains". XMPP already does federated IM, since long before the current fad.
I match any vague handwaves about identity or security with vague handwaves at existing SSL certificate authorities, and an observation that if you're going to complain about the security of such things I get to apply an equal amount of effort towards breaking your blockchain solution, e.g., if you're going to complain about nationstates getting root certificates they shouldn't, I get to point out your tiny little blockchain for IMs is equally vulnerable, if not more so.
Though I will concede your point slightly; if XMPP needs some more Hype Juice to win, I can't deny "but on a blockchain!" could help there. Kinda not being sarcastic here.
To the declining popularity of Jabber, to put it short.
As an additional benefit, blockchain is indeed more secure to run than an ejabberd instance.
I understand your irony with "Hype Juice" etc. But in the end, good software is that which people use, right?
just this week I saw https://adamant.im
There was a thing called "my echo" (which appears to have failed/been cancelled).
Other related things are fine: e.g. mapping public keys to human-readable identifiers like a nickname is a good match to what a blockchain is good at, I get why people like the idea of cryptocoin-payments in a messenger platform, ... Still leaves the general concern of "does this really need it's own coin with an ICO and hype", but at least the ideas make some sense there.
However, from my understanding of Telegram's ICO and "leaked" roadmap, they appear to be doing a decentralized chat the may leverage their own blockchain for some features (identity, tokens etc.).
I think Status.im is another example, but it's currently early access I believe.
My own product, stealthy.im could be another example. The web product is in production. It builds upon blockstack, storing identity and storage pointers in the blockchain.
So that's 3. I could probably list a few more, but again they wouldn't strictly satisfy your precise criteria in one or major ways. I think @jerf's response is really good--for us the "why" of blockchain is in identity and providing a verifiable decentralized storage network through blockstack. The underlying bitcoin blockchain wouldn't be suitable for message storage or sdp handshaking due to latency as another person pointed out.
I hate this mindset