By mainstream do you mean television and billboards? Maybe it's just a fluke but I seem to get tons of Google Chrome ads on the internet on youtube, pandora, etc.
On blip.tv, I've been getting ONLY Chrome ads for a few days. Nothing else. It would be great if they could auto-detect that I'm already running Chrome and run something else (if they have anything else in the inventory)...
It's possible that you don't fit into any other segments and that Chrome is the fallback advertisement for blip.tv. Do you happen to have 3rd party cookies disabled?
In the UK I've seen adverts on TV, Billboards and online. That's a heck of a financial commitment from google to building marketshare.
Having come back to London after the holidays today, the tube (metro) is plastered with adds for Chrome again (they've pushed it quite strongly before, but this seems to be a new push).
I saw a Chrome cinema ad before Tron (UK as well).