No, it hasn't already happened. The shit on public surfaces is illegal advertising, like plastered posters, which is not big corporates. This is just as bad as graffiti.

I am not arguing against freedom of speech, what I am saying is that one person's rights cannot override another's. Everyone has a right to clean public spaces, why exactly should a graffiti "artist's" right to express himself override everyone else's rights?

And don't tell me "because the big evil corporates are doing it" because firstly, they're NOT doing that, and secondly it's just saying that two wrongs make a right.

Or arguing that the best way to protest against murder is by going out and killing people.