WeWork, a company that offers shared, flexibile-lease offices in 113 locations in 33 countries, has achieved a position in the "coworking" world similar to that of Starbucks in the coffee world. While plenty of smaller companies offer coworking in a myriad of flavors—focusing, for instance, on designers or startups—they’re not a significant threat to WeWork’s business. No Dunkin' Donuts has emerged. A bigger potential problem for WeWork as it strives to live up to its $16 billion valuation would be if the landlords and companies it works with build their own hip office spaces.