As advertising permeates into more parts of our lives, people learn how to block out advertising, develop blind spots, which prompts advertisers to find yet more ways of cutting through the clutter, leading to a self-propagating cycle of more advertising and less ad-free non-commercial space.
Italian agency MTN Company recently used zebra crossing advertising to promote an architecture and design event called “Settimane dell’Architettura e del Design” (via I Believe in Advertising).
See the pictures on Flickr (they are not shared under a Creative Commons license, so do think twice before you put them up at your blogs) —

– or watched the making of the zebra crossing ads on YouTube –
The ads are done really tastefully and add to, rather than take away from, the public space they use as a platform. The Sentieri Urbani project, for instance, uses a similar street art approach to to beautify public space. My experience, however, is that it doesn’t take long for an innovative new medium like this to devolve into lowest common denominator space. It’s one thing to have black and white flowers and hearts on the zebra crossing, it’s another to have loud multi-colored “Buy Now!” price and promotion ads.