[threwaway4392]

Here is another incentive:

When users share their bills and EOB, provide them with an automated analysis of their bills: what seems weird, which billed items were far above average prices, etc.

This information can be precious when negotiating with the doctor's office, when Yelp/google-maps reviews, or when contacting your politicians about the absurdity of health care costs.

[dizzant]

This is an excellent idea. Also, sell aggregated data on cost of care in local areas to doctors and insurance companies, so they can make clear business decision on how to compete against the local market.

[EamonnMR]

Though that creates an incentive for the company to not share its own data.