Focus. Both from my own ventures now and from start-ups I've worked with previously in the past, I see focus as one of the largest needs of a start-up.

Without focus, successful start-ups move on to too many fields, dividing their resources amongst too many projects. Early start-ups can distract themselves by losing sight of the primary issue they're aiming to solve and losing traction on those core concepts can be a death knell.

Sadly there's no easy way to outsource focus :)