My question is, if your site requires a login to use, then Google Adsense will display security and password/login targetted adverts because the google crawler doesn't have a registration on the site.
Therfore, is it possible and legal (within the boundaries of the adsense program policies):
Obtain a list of IP's the Google crawler uses, and when it's detected the computer viewing the page is the google crawler, dont display the login page but keywords targetted at what should be displayed if you were logged in.
Or for that matter, is it ok to do that with keywords unrelated to your site completely (higher paying ones?)