Its rare that everyone is on the board, even more rare that everyone has the same level of excitement for the company.
Too many times one person has the ideas and brings on a second person to help only to find out that person can not hold up the agreement or does not have the commitment to make it happen. Having them on the board is then a huge issue.
If its your company and your money, be careful who you let on the board. If you need "Adult Supervision" as required by an investor then thats different but keep as much control as you can, you don't want to have Gi Joe wearing Barbie outfits if the business is making commando clothes, its your dream and you need to control it.