It's not that easy. What if the MPAA, Playboy, etc. send file filenames to Google and say "It's illegal to link to this file and if you do so, you are willingly and intentionally violating our copyright" Is that really what we want? It's a slippery slope when courts make these rulings without really understanding the impacts.
"What if?" That's already what happens. Google puts up a notice that some results have been omitted due to DMCA requests and links a copy of the requests.
