I'm part of the OpenStreetMap sysadmin team...
We think it is great that Bing is using our open map data! Hell them using our data is great promotion for our project.
We currently have no need to ask them for anything back and I'm sure if we tapped them, they would be supportive. Our project is about creating great open map data, not about becoming rich.
Is Bing working on improve OpenStreetMap's open data further? Quite likely. They win, we win.