In a related point, there is a law in effect here in the US that affect most websites. I'm working on updating content on several large websites for this change.
The California Internet Privacy Bill. Our legal counsel has boiled it down to the following points.
If any consumers of your web service are located in the state of California, you must:
- Explain "how you deal with" do-not-track requests.
Now, this doesn't mean you have to "do" anything about do-not-track requests, you just have to explain how you deal with them. That could be statement along the lines of "We take do-not-track requests and promptly ignore them" - but if you want to be compliant, you need to say something somewhere and link to it.
All that said, how the state of California plans to take action against the the millions of non-compliant site owners is another question. Presumably, you're going to have to be a pretty big fish, and be flagrantly non-compliant, to get any heat on this. (note: this is not intended to be legal advice : )