Not among allies. If you can spy on everyone but your own citizens, you only need 2 nation-states cooperating to spy on everyone. Which is already occurring at a minimum between Britain and the U.S.
There's no easy way to prevent the sharing of the private information of civilians without some kind of exception, and that exception cannot be precise without artificially limiting the intelligence capabilities of a country, which in practice will mean such a limit will be ignored, or, more likely, will have an easily abused exception (i.e. terrorism) to make it more or less toothless.
No they won't. The problem is countries you wouldn't even expect to will trade data to get around domestic spying restrictions. If, say, the US compiles big databases on German citizens, and the German government does likewise with Americans, German and American spies can trade and thus get their hands on data they would like to have but can't legally collect.
Once your data is out there, it's out there.