Diversification is a sign of robustness. A diverse investment portfolio is less prone to risk. If you have more than 1 professional skill – say you’re an accountant and a great chef, even if all accounting jobs are outsourced from your country you still have another skill to count on. A columnist in 1 newspaper is vulnerable to that newspaper shutting down. If the columnist writes in 10 newspapers, even if 3 are shut down, she is fine.
With relationships, diversification doesn’t work as well. You’re better off with 5 true friends rather than a 100 superficial ones. You’re better off with one life partner rather than having to change every now and then. As a venture capitalist, you’re better off making a focused bet in a sector rather than diversify spray and pray.
Whether to diversify or not depends on your time horizon. How long do you wish to play the game? If it is one or two years, then diversify by all means. If it is 10 years or more, put your eggs in one carefully chosen basket.