It's a pretty silly story. To keep even 10% ownership of Box through their massive dilution would have been extremely expensive. Cuban owned a small position in it. Very understandable how that would not have been worth it for a guy like Cuban (who has demonstrated he's content with a couple billion, and never puts even a small % of his fortunate at risk, having stated over the years that his biggest fear is losing it all).
"DFJ got in early, contributing the whole $1.5 million Series A round in 2006, and participated in every round after to build its 25.5% position. The Wall Street Journal says the latest $100 million round was at a $2 billion valuation, which implies Box will likely be valued higher than that at IPO."
Cuban invested $350K in the seed, so it was just his call.
