After Mapquest, it's now Bing's turn to add OpenStreetmaps
http://www.bing.com/toolbox/blogs/maps/archive/2010/08/02/bing-maps-adds-open-street-maps-layer.aspx
http://www.wired.com/epicenter/2010/08/microsoft-adds-openstreetmap-layer-to-bing-maps/
Since Acme mapper got the Google maps and Openstreetmaps(via Mapnik) layers, it could be interesting to wish then Acme mapper add a Bing maps layer as well.