[auganov]

Well for the vast majority of simple apps you're better off failing when everybody else is. People will blame it on you less. When your alternative solution fails and everything else seems to be up the blame will fall on you.

[Kaknut]

I always prefer to have a backup solution which could at least crawl during these situation if not able to walk. I see many SaaS relying only on google/twitter/fb auth but they need to understand that having own system too won't harm them much.