Rural southern Ontario doesn't have the best quality Bing imagery, likely due to its low population density. But the USGS does, so if you set your background to be "OSM US USGS Large Scale Aerial Imagery", you'll be more likely to map accurately from it.
Not quite sure what to use as the source tag, though. USGS? Updated: Thanks to Sanderd17, it should be source=USGS Ortho.
Note that this imagery doesn't go very far north into Canada; it's definitely not available up in Algoma.