Moreover, social logins are often implemented in an insecure way. Users, in this case, have to trust every application which implemented this feature to handle their identifier confidentially.

A good heuristic is to not trust the libraries you did not write either.

he goes on to talk about third party problems and how you're never guaranteed something is written correctly or that even if it is you don't know if it's the most optimal solution

that's a point, but I would say the opposite, when entering credit card data I would rathre prefer to be entirely in the Verified By Visa (Paypal) webpage (with the url easily visible in the address bar) rather that entring my credit card data in an iframe of someone's website.

I'm very (VERY!) tempted to use that ppa, but without offense to it's maintainers... it's just some random ppa. If it had more "traction" I'd use it. Right now it has only 3 maintainers.