Google ads have recently appeared on websites you haven't authorize

It's okay to allow those sites. I do. They are part of
google's system.

Most of the time it has to do with the google cache, or
google showing your site in another "way." Like if you
have a blogspot blog. If you blog is at blogspot.com,
but somone in India views it, google will put the .in
at the end of the domain, magically making your blog
a .in website...so you simpley add yourblog.blogspot.in
to the okay sites.

The wayback machine will also shows adsense sometimes,
so you get that message as well.

Yahoo has their own cache, so I add that as well.

Perfectly okay in those cases. There are other cases where
they put your site in some frame, and it looks as if your
ads are appearing there. Perfectly okay to add them if the
parent site makes sense. That's the key. You don't want some
porn site showing your site or something.

If you are ever in doubt, just do a search for the site. Others
have asked the same question, so there is a lot of info.

Of course there's nothing wrong with not authorizing them.

I do allow the google cache. People do use it if your site is
not online at the moment. Not a lot, but who knows. Might be
worth a click.

Paul