Windows 8 is crossing that line by showing you ads through no additional action of your own. The real debate amongst commenters here seems to be whether this is a major line, or just another one in the long list of those already crossed.
You can visit many parts of Europe to find less visual clutter. Even here in the US my county bans all billboards except one, so it is quite jarring being elsewhere in the country and seeing how prevalent they are.
I must admin being astonished at American's tolerance of advertising. Somehow people are averaging 5 hours of TV watching a day, yet the broadcasts seem to be non-stop advertising briefly interrupted by snippets of programming. Web pages seem to be substantially similar.