Buy-in;:  Although it may seem obvious that including others may be the key to getting buy-in, too many planning processes limit who gets included.  Simply put, plans we have a hand in creating are more motivation to us.  A key human motivation is control - we like to feel like we have some say in our destiny.  

Visibility; Marketing; Information; Attitudes: Including stakeholders  at all levels within, as well as outside the organization (customers, vendors, community members and leaders) is another piece of the engagement process. Although they don't have to plan, they can be asked for input, through actual conversations and surveys.  Asking widely provides extraordinary opportunities for new information, and important perspectives and attitudes toward your company. Including outsiders also provides an opportunity to build visibility - a marketing tool in a way. You don't want them all in the planning process, but you do want them in the exploration stage!  When you ask people their opinions, they get more interested, more engaged.