For the time being assume this service exactly matches your needs in terms of functionality, price, user experience etc.
What would need to be in place for you to actually trust the service with your data and to give you confidence that the service will outlive you?
What protocols could the service put in place to ensure that its fail proof? These could be tech protocols or in-person protocols.
I'm not a programmer so I'm thinking more in terms of non tech solutions like giving users voting rights and promising that users will maintain 51% control, or something to that effect. But I feel that there must be more developed and robust solutions to this question?