Caltrans has a "Maintenance Service Request" web page at:
If they get enough requests, maybe Caltrans will remove the shoes.
(relevant info: HY 101, San Mateo County, Redwood City, X-st Marsh Road, Southbound, category Graffiti or Litter)
Shoe flinging is a form of graffiti and vandalism: Just as with graffiti, removing the offending eyesore is the way to keep the problem from getting out of hand. I know, I know - Caltrans is short of money, but it will cost more in the long run if copycats fling more shoes onto overhead wires.
Probably this is just a juvenile prank, but at worst shoes on wires mark gang territory. Copycats risk their own safety and the safety of traffic while flinging the shoes up there. And if left untouched, the shoes will eventually fall down, with some chance of injuring someone in 70 mph traffic.
The city of Chicago (police and street maintenance)takes shoes on wires "very seriously" and through abatement saw a 50% drop in the incidence of such vandalism. See
Abating graffiti and vandalism is important, and constructive suggestions are welcome. Who else should we contact?