OK Go, the most downloaded band ever, will launch an extensive North American tour with a performance at the Los Angeles County Fair on October 3rd. Tickets are on sale now. In addition to its headlining dates, the band will perform at the Discover Louisville Festival (10/12) and the PopTech Conference (10/21, Camden, ME), an annual event that convenes a network of visionary individuals in science, technology, design, the corporate and social sectors, entrepreneurship, education and the arts to explore…