A history of shutting down site-identity related products, no less. [1] The fact that it's not on Android as of day one looks pretty bad too; the sort of developers who think iOS obviously comes first are (in my experience) likely to be chasing hype and their apps are dead in a year (or at least still not on Android). I don't know if that's the case here, but I have no interest in using this until it's been adopted by Mozilla as more than an experiment and has several years of strong support.

[1] https://developer.mozilla.org/en-US/docs/Archive/Mozilla/Per...

(I admit I'm biased here but I'm still bitter about them nixing Persona.)