In the state of Virginia, bikes are allowed to ride on roads, except highways, with the same rules as cars. They are a waste of money and paint and they give some bikers the idea that they have special privileges in these lanes, potentially putting them at risk. Cars basically ignore them and many times they are placed in lanes that have parked cars in them.
Additionally, in areas where there are right turn only lanes, the sharrow puts bikers in the middle lane. This is due to a State law that says bikes can't travel in these lanes. But without a protected lane and some kind of signage, the biker is left to fend for themselves between lanes of traffic. Sometimes these turn only lanes are on/off ramps for highways. Motorists are typically much more aggressive when they have to deal with entering or exiting a highway.
To illustrate what I mean, here is a video I put together illustrating my commute on the Boulevard in Richmond, VA.