What exactly is Azure Active Directory B2C?
Cloud identity service with support for social accounts and app-specific (local) accounts
For enterprises and ISVs building consumer facing web, mobile & native apps
Builds on Azure Active Directory – a global identity service serving hundreds of millions of users and billions of sign-ins per day (same directory system used by Microsoft online properties – Office 365, XBox Live and so on)
Worldwide, highly-available, geo-redundant service – globally distributed directory across all of Microsoft Azure’s datacenters
I am a big fan of OAuth and making it easy for line-of-business developers to deal with authentication (lest they get harebrained ideas like rolling their own encryption algorithms).