High growth comes with more complexity and greater risk. A feature from YEC Quarterly Magazine. Human resources software company Zenefits had everything going for it. Within a year of its 2013 launch, it had raised over $80 million from leading VC firms and gained over 2,000 client companies across 47 states. By 2015, it reached a $4.5 billion valuation, making it one of the fastest-growing SaaS businesses ever.