The best entrepreneurs, from what I have seen, are the people that want to and must be involved in all core business responsibilities. The passion and persistence required to create something demands this.

However, I believe there are exceptions to this, such as design. If you have great product vision, technical ability, understand your users and you are infinitely passionate about the product you are building, I see no problem with outsourcing (at least initially) to 99designs or similar sites.