A small but growing number of founders are betting on bringing people together offline

Brynn Putnam and Tristan Walker have already done something that most founders only dream about: created companies so compelling that bigger outfits bought them. Putnam, a trained ballerina with a small chain of boutique studios, built the connected-fitness company Mirror and sold it to Lululemon for $500 million in cash less than three years later. Walker, who interned at Twitter while at Stanford business school, built the popular men’s grooming brand Walker & Company Brands, selling it five years later to Procter & Gamble for undisclosed terms (reportedly in the range of $20 million to $40 million). That both of them are at it again is less surprising than what each is building. Founders tend not to love working inside other people’s companies — Putnam has hinted…