ALL online aerial mapping sucks. I've had positional errors from 20 ft to 5 miles! 20 ft is acceptable when you bear in mind that ALL of these services were primarily designed for GPS navigation. In the context of Bing's market philosophy, civil design isn't even a blip on the radar.
If you need real aerials for something more precise than county level planning, get real orthorectified aerials. In Fl, FDOT and many counties have decent sid files available for free. Still GIS grade, not survey quality, but better than the online.