Hi, I'm a Mac, and this is the message from my sponsor.
Steve Jobs is the inventor of OS advertising, according to the patent application #20090265214 "Advertisement in Operating System" submitted today: "Ad advertisement presentation may occupy the entire screen so as to prevent the user from engaging in any desktop activities. To verify user presence during the presentation of the advertisement, in some implementations, a message maybe populated, on a schedule or random basis, which may require user action or confirmation. As an example, a message may be populated which may require a user to click on the message within three seconds."
Love the UI mock-up.