About ads and service

On my way to the Provincial house for my retreat as I viewed the plenty of ads and bill boards covering every bit of public space along the busy roads, an idea struck me: why not make every advertiser (especially bill board users) use 20% of the ad space for a public service message. It could very well be in line with the product they are endorsing. In that way, a social service message too will be delivered along this otherwise purely commercial lines.