I'm gently worried about the spam vs ham problem. Some people must not ever have a false positive.
In theory this law encourages good companies to stay good companies and to not outsource to dodgy spam outfits.
It is weird that in 2012 we're still making up stuff about the best practice for sending email.
You might claim Gmail is worrying about the bandwidth, but again: this kind of spam is a tiny tiny fraction of the spam problem. These people are already capable of using buttons that say "spam": a killfile is just another single-click button.
Finally, and again: the spam vs. ham problem is mostly complex because people are misdefining spam as "mail I don't want" as opposed to "mail I couldn't possibly have wanted" (and thereby use the spam button to punish people whose policies they dislike, which both mistrains filters and relies on machine learning to solve a straightforward problem that could be exactly solve by rules).
The spam in the latter category must be machine filtered, as this law, nor any other possible reasonable law, doesn't make even a small ding in it, while the remaining spam in the former category can be handled with one-button killfiles.