> where the Google front page feels like a public space, the logged-in side of Gmail feels more like a private area. This means that while a holiday Google Doodle sails by just fine, a reminder in Gmail feels very invasive.
One reason for drawing the distinction between what feels like a public versus private space is based on the private information that is contained within gmail, versus the non-private information on the frontpage.
An additional reason that gmail may feel like a different area than the frontpage is that Google doesn't often make modifications like today's (I don't use the chat functionality often so I am not sure if they have done other modifications similar to the call reminder today). Users who were offended by today's reminder but not by today's frontpage doodle might have found the doodle offensive if Google had never modified the frontpage logo, or modified it less frequently than they currently do.