Fred Wilson venture capitalist and Co-Founder Union Square Ventures
“Every company should have a Board of Directors.  [Benefits] include  advice, counsel, relationships, experience, and accountability.
[Shareholders] elect the [Board]  [usually via] a nominating entity that puts directors up for election by the shareholders. 
[Wilson likes] a three person Board early on in a company's life [including the founder with two others he trusts and respects].
 [Investors sometimes negotiate a Board seat - less common for angels, moreso for VC’s].”
A founder can still control a three or five person Board. “As a company moves from founder control to investor control, [an independent director is considered].  [Wilson likes] independent directors . The more independent minded the Board , [usually the better].
[Wilson argues] that an investor controlled Board is the worst possible situation” since an investor’s interest is narrowly his financial return, not a broader company perspective. “[Investor directors should not control the board.] The founder should control the board in a company he  controls and independent directors should control a board where the founder does not control the company.
 [Boards should evolve, recruit new members regularly and have term limits]”, preferably 4 years.
“Most importantly, build a great board.” Fred Wilson, The Board Of Directors - Selecting, Electing & Evolving, Mar 12, 2012; http://www.avc.com/a_vc/2012/03/the-board-of-directors-selecting-electing-evolving.html