> There is now way to know if you have +1'd a page without sending your unique id with.

localStorage or asking which URLs have been plus 1'd, not the other way around. There are plenty of ways of doing it without sending a request back to google on ever. single. page. load.

I found the disclosure about all website visiting being sent to Google only after looking for it and clicking through some pages. 95% of users will never find that since being alerted to it isn't part of the standard install flow.