Yelp CEO Jeremy Stoppelman. Yelp is one of the few internet companies of its generation still run by its founder. Photo: Amy Osborne/Associated PressBuying growth is rarely a cheap concept, especially for small tech companies that lack the pocketbooks of their much larger peers. Yelp knows this well. Founded 19 years ago as a pioneer in the field of online reviews for local businesses, Yelp has established an Internet advertising business now generating more than $1.2 billion a year in revenue. That is a 10 ...