Yesterday was clearly one of the two days this week that Google/T-Mobile’s G1 ad campaign was pumping out impressions. We know that this was rated at a billion impressions — or a significant amount of Platform-A’s inventory — in that timeframe. My initial response to this was that such a large buy over a short period of time was more about brand advertising in the weeks coming up to the holidays than it was about CTR and other direct-response measures.

After sitting on the train yesterday evening, I have to second my own thought. What are the brand implications of having placing a banner on every single laptop on an Amtrak train? It’s definitely powerful.

I’d seen copies of the G1 lying around the office, but I’m the media guy, and my co-workers generally keep me away from things that I can (and will) break. So I really haven’t spent much time with the first branded incarnation of what has otherwise been Android.

That definitely changed yesterday. Sitting at the back of the car, I looked up from my computer and saw two dozen computer screens, everyone browsing the web, and G1 banners and leaderboards on each and every screen.

Come to think of it, it’s not only brand. It’s digital out of home. That’s two digital birds with one media plan.