Other then Center City I've seen these start to appear 2 years ago, I made complaints to L&I via the 311 system and of course got no service. As I suspected they began to multiply like cockroaches.
I guess because the companies dropping them off at every corner feel like they are doing some type of "Service" for the public they are exempt from the law. Of course the inaction of the City doesn't help matters.
It just pisses me off that nobody cares about the small things that matter to some of us.