DCist: the city has eased regulations regarding posters for events -- now they can be up any amount of time before the event, but must be taken down after 30 days. Before I've complained about the ANSWER posters that are up forever after the event. The group was fined a number of times for not removing posters.
The rule change stinks. If I've learned anything about poster putter-uppers, it's that they don't mind covering the neighborhood with posters and then not removing them.