Let's say there is a website X, providing some kind of information or service. I am not their registered user, do not go to their webpage. I open somebody else's webpage Y which somehow incorporates content from X. For example, the site I visit has a Facebook Like button, or shows a Vimeo video, or a Google Maps interactive map.
At that point, am I a customer of Y, or both X and Y? Am I bound by the Terms of Service of X in some way? If during my browsing Y I somehow reveal data to X, are they free to use it in ways to which I never agreed consciously (but are covered in their Terms of Service which I did not read)? Also, if X has data about me from another source (say, they know my e-mail address because my best friend allowed them to scrape his contacts), can they now treat this data about me the same way as every other customer's?