What are the advantages and disadvantages of selling Shares to the public?

Answer 1

If your talking about a private company going public --
Advantages: Raising money. Establishing a management level (board of directors) help in company focus, for transfer of leadership, etc.
Disadvantages: Losing ownership power to board of directors who are (or at least should be) responsible to stockholders, not you. Lots more government regulation.

Answer 2

Shares are sold to the public largly to cash out the original owners. More shares are issued in an effort to raise more money, but this dilutes the value of the other shares that are already in the market