A couple of weeks back, I came across the Google home page and it was reversed out - black where it should have been white. At first I thought that my MacBook display had given up the ghost, but luckily for my wallet it hadn't. It was Google's contribution to the lights off energy saving initiative...
I didn't think anymore about it for another couple of days, until I saw a photo in the newspaper of European capitals in darkness (apart from - scandalously - London!!), and only then did I realise that it was part of a wider campaign.
But then I wondered how much more potential visibility the Google page had than the fact that the Coliseum was blacked out for one evening? Apart from the fact that Google use far more energy keeping their server farms up and running, than you'd think; they must have reached millions over the course of that day.
And should you be interested, unlike the other parts of the campaign, Google would be able to tell you EXACTLY how many people had seen the lights off message on their page.
Which is a long way of reminding you that your online marketing can be monitored and refined through that monitoring to perform better. Are you learning the lessons of the old direct marketeers? Or do you just assume that its working?