I am tired of repeating this again and again, so I am doing some yak shaving and creating a hosted rest service for managing user accounts and authentication. I will use it as basic infrastructure for future projects.
Rather than a hosted/solution - I would be think a program language specific (node/php/java) solution would be more useful. For example - something like $199 for lifetime use for account/oauth/etc system that you can use on any project. Maybe even have additional "packages" like invite friend, etc. Just a thought.
