I've been riding my bike each evening after dinner. Pedalling along the sidewalk that is flanked by unkempt landscaping helps me to burn the calories and help my bad back. Either the developer is a slug (and he is) or the county can't afford the maintenance (they can't) - but I have to get off my bike occasionally and push the goathead weeds off the sidewalk and back to the dirt where they started. This practice will, no doubt, have to continue until the (ir)responsible party takes responsibility.
When I was a kid, we would intentionally step on these so they would stick in our Keds so we could have tap shoes. It wasn't fun to land on these with flip flops or barefeet. It's no fun today to have these boogers jammed into my bike tires.