Those blocks will come down really quickly if business owners started getting fined for putting them up and van-dwellers started finding their houses getting towed. However, the city likely can't do one without the other.
My suggestion: If debris was left in front of my property irrespective of whether it was within my property or not, I’d get a notice to rectify. If I didn’t within a reasonable time frame, the city would rectify it for me and send me the bill. Failure to pay the bill within six months would simply result in it being folded into the property taxes. Consequences for not paying taxes don’t need explanation at this point. Very effective strategy. Not my fault someone dumped something in front of the house, but how to track who did it? Easier to shift it onto the property owner.
In my case I would simply put up security cameras that are clear enough to pick up license plates. The city would be only too happy to pass on the bill to the vehicle owner of whoever dropped off the crap.
Context and proportionality are important too.