Foursquare co-founder Naveen Selvadurai and Big Web Show host Jeffrey Zeldman discuss mobile apps and the quantified self; the genesis of bookmarking places; creating mobile UIs in the bad old days before smartphones; how Delicious’s bookmarking helped inspire Foursquare; what was really innovative about the iPhone from a mobile developer’s perspective (it’s not what you think); when to quit your job and start a product or service; where ideas come from; and what’s after Foursquare.