In a previous life I worked for an ad agency and we always tried to steer our clients away from billboards. The cost is too high and the ROI is too low. They're usually an ego buy.
Generally I want to agree, but it depends on the product. Some things are custom made for billboards, like "McDonald's, next exit." Anything that's not primarily about location (next exit), is probably a waste, or would require a massive purchase of space to flood a market, which, like you said, would probably result in a lousy ROI.
true, that's the difference between a Call to Action campaign vs Brand Awareness. A call to action has a specific request (exit here for food, call here for tickets) where as the brand awareness would just say McDonalds, I'm Lovin It or OHIO. My Team. My State., etc. The Buy Tickets boards could be effective within a certain radius of Athens though.
but, the more I think about it, a big ol' My Team My State billboard could have some value if you stuck it in a controversial area, like right by another school's campus or strip of bars. Something that would create a bit of a stir. Like a big green middle finger in a sea of scarlet and regret.