Your identity is on the blockchain and that is decentralized so even in that case you or anyone can run a separate node to handle them. Also all the auth library is open source so anyone can work on that.

Its a distributed database, it doesn't matter if the blockstack company takes a long walk off of a short pier.

Many things are free to sign up for. Heck, I regularly sign up/join any Show HN-featured site.

But there's zero reason for any site not to offer the tried-and-trusted email and password, even just as as a fallback option, especially these days where trust in online stuff is seemingly at an all-time low.

Google, Facebook, et al., companies with massively larger, dedicated security departments swore up, down, and sideways that "everyone's data" is "secure" and "encrypted" ";)"