I disagree. Since most trails I have used are festooned with some sort of sign post anyway why not make it useful? Most trails are maintained by volunteers so there is no labor cost to install it. I would imagine the company negociates on quanity/cost per unit basis so if two trails/MUPs near each other comingle their purchase the cost is lower. Lastly how often have you been out on the road/trail and had a flat and had to lay your favorite bike down in the dirt or even worse the mud?

I don't think they need to be every 100 feet along a trail but one in parking area and maybe between parking areas is not a bad idea. Certainly this is a good idea for a business or school with a large cycling population.