In Billboard War, Digital Signs Spark a Truce - WSJ.com

"For years, Clear Channel Communications Inc., a giant of the U.S. billboard business, often won the right to put up big signs by dragging cities and community groups into court. But in Cleveland, one of those court fights allowed Clear Channel to soup up its signs and win over residents at the same time.
The reason: In a settlement, Clear Channel won permission to put up lucrative new digital billboards along highways in return for taking down some old-fashioned inner-city billboards. The new signs flash a sequence of ads from seven different companies, multiplying Clear Channel's revenue. All over the country, billboard companies are racing to transform venerable road signs into these high-tech moneymakers. As they do, they are changing the dynamics of civic battles that date back more than a century."