> Wait? When was Kik ludicrously popular?
Kik was ludicrously popular among 16-24 year olds (and, both sadly and notably, I believe people even quite a bit younger); one of the main reasons cited is because your parents couldn't find you easily using your phone number (as they could on WhatsApp) or your real name (as they could on Facebook), etc. FWIW, I'm way too old to have used it myself (and was just as shocked at how popular it was as you seem to be when I learned of its existence at age 36).
> Usernames clearly wasn't a feature that kept users coming back as the service almost shutdown in October before being sold off.
I mean, the story is that Kik had a hard time figuring out how to monetize its user community, particularly given how many kids were using it, and so they decided to try launching a cryptocurrency at the height of the crypto bubble in 2017, which led to a $100 million dollar fine from the SEC due to irregularities in their offering... they got to the point of being so screwed that they decided to try crowdfunding their legal defense against the SEC, and so shut down Kik and fire most of their staff to conserve cash (where they were still in the "lose money on massive growth" phase of "maybe one day we will figure out how to sell ads or get bought by Facebook" trajectory).
However, that's the story; when I started looking into it (as I cared a lot about their SEC issues, as someone else who was working on a cryptocurrency project) I noticed they were also under some serious investigation for what was looking like child trafficking on their largely anonymous network of kids, and so one might want to consider the idea that this whole SEC SNAFU served as a good excuse for shutting down a business arm that was actually about to land them in much hotter water with the FBI than their offering was landing them with the SEC without actively coming out and saying "we looked into it and uhh... it was bad". Either way, AFAIK they didn't shut Kik down because it wasn't popular.
> Also, who wants to fight for usernames again?
Usernames aren't the only way to deal with identity. I'm not advocating for usernames (and in fact have some serious issues with them: I have on many occasions--all of in talks, on panels, and in comment threads--argued that the usage of permanent and unique chosen identifiers is actually immoral for a number of reasons I won't delve into again here), but the idea that phone numbers are somehow fundamentally better--particularly this argument comparing them to e-mail addresses--makes no sense given that essentially no other popular social network bootstrapped off of your identity being a phone number; the closest you could argue is that they supported mass address book contact matching, but that was always optional and somehow those services succeeded.
(Really, I think the argument Moxie was making was just fundamentally flawed as it was a broken analogy: he was trying to compare it to e-mail addresses as if e-mail were the competitor, but most people treat e-mail as the backdrop reality of identity not a viable competitor to their real time chat app, whether or not you want to argue they "should" see those as competitors. He then just fails to really tie the argument together with how any of these other social network services bootstrapped, and comes to this conclusion that the phone number is somehow the perfect identity. Like, if you compare phone numbers to e-mail addresses from the perspective of a service that is neither a phone company nor an e-mail service I think you get a very different answer than if you compare Signal trying to rely on third-party phone numbers to e-mail services relying on first-party e-mail usernames.)