It's Instagram's fifth birthday, and to celebrate The Guardian despatched me to California to meet Mike Krieger, its co-founder. Our 30 minute chat is available to download HERE. For a dotcom billionaire, he's incredibly modest, and full of sage advice, e.g. "You should be able to explain your startup to a stranger at a bar" and "People who live in Silicon Valley are living in a future that is never going to happen". Too true!