So what happens to my users if your service ever goes down or disappears?
> MePIN comes as a distributed hosted service containing simple-to-use REST API and handy client side scripts. Hosted or in-house white label solution is also possible, contact sales@meontrust.com.
"What happens if/when these fellas implode?"
The answer in the site's case would be to fall back to SMS. Something like this that could be integrated into the site itself would be better, working in tandem with a more typical fall-back of course.
Other than that; You own your users and user database. No user data is stored at MePIN servers.