[rcamera]

I work at a company that prints tens of millions of photos every year, and that has a Facebook integration app.

Actually, the image quality you get from FB through their API is dependent on both the photo size that is being uploaded, and the quality you ask facebook to save your photo at. A high resolution photo that is uploaded to Facebook in high quality mode is a good photo for a 10x15cm print. Any bigger print size and you start running into resolution issues.

The trick here is to show the user which photos he will have low resolution issues, and which he won't.