Effective Oct 1, 2011 there is a new Maryland law that makes it easier for the state to enforce the prohibition on signs in state right-of-ways. It also explicitly gives this authority to the Counties. Harford County has begun a volunteer program to remove signs.
<a href="http://www.baltimoresun.com/explore/harford/news/ph-ag-state-laws-0928-20110927,0,7613590.story">Story</a>.

I'm hoiping that Baltimore County will soon pass a new law to make it easier for citizens to pick up signs.