The growth of a company is limited by 2 factors: 1: How influential the company is on the market and to their userbase, and 2: How well the company operates their business. These 2 factors are something Bitfinex has done really well for so long, and their dominance on the market is a representation of that. Small fees, a well structured website and API, simple interface wit hthe possibility of a more "complex" personalization if you so wish, efficient customer support, and the safety of your funds being guaranteed by the sheer ammount of security measures Bitfinex applies. A happy customer for a year now, and for many years to come.