These signs, and a lot more, have become almost permanent fixtures along the 5/405 corridor in Orange County, California - a hotbed, to paraphrase Abbie Hoffman - of social rest.
Maintaining at least five lanes of heavy traffic in each direction, Interstates 5 and 405 host hundreds of thousands of drivers per day in Orange County. Of course there's no telling how many of them keep up with Supreme Court rulings or know about the Citizen's United decision, but I figure that those who don't simply have their commutes made a little more surreal, or assume that someone's merely stating the obvious. In this respect, even the most uninformed drivers have a clearer sense of jurisprudence than Scalia, Thomas, etc.
I paint my messages in different sizes to adapt to a variety of posting spots. The signs above took about two and a half hours to make and cost... practically nothing. The cardboard was free out of dumpsters and I used probably no more than 47 cents worth of paint and duct tape for the lot. The bicycle on the far left will give you an idea of the scale.
Because of the layout and infrastructure, OC postings are best kept to the sides of the freeways, a vast and easily accessible no-man's-land of fencing and iceplant. This rule holds true pretty much across the board: the signs that are read the most are the ones that stay up the longest. Smaller signs placed along the peripheries of freeways will stay up for days, weeks or even months compared to overpass postings.
"I'll believe corporations are people when Texas executes one of them." -Sign at Occupy Wall Street