On some streets, bicyclists riding over the sharrow marking will take the entire lane. Aren't they suppose to move to the right?
Not always.
According to Virginia State Code Section 46.2-905, bicyclists are to stay to the right when riding less than the normal speed of traffic except to pass other bicyclists or vehicles, to prepare to make a left turn, when necessary to avoid conditions (including fixed or moving objects, surface hazards, or substandard width lanes too narrow for a bicycle and vehicle to travel side by side) that make it unsafe to continue along the right.