Limited liability. Your only risk is capital paid into the business. Business debts and other liabilities can't be squeezed out of your personal assets. Caution: If you personally guarantee a debt, you've forfeited your "limited liability."
Tax simplicity. Profits and losses are reported and taxed on owners' individual returns. There's no separate business tax return, unless you have more than one member and choose to be taxed as a partnership (Form 1065). And there's no corporate "double taxation," in which both the business and the shareholders are taxed.
Flexible management. A "member" (shareholder equivalent) can be a person, partnership or corporation. Members get a percentage of ownership. If your idea people can't manage their way out of a paper bag, you can hire management help. Smaller LLCs are usually member-managed, but not always.
Flexible distribution. Profits and losses don't have to be distributed in proportion to the money each person puts in. A regular C corporation can't allocate profits and losses. And in a subchapter S corporation (taxed as a partnership), profits and losses are in proportion to shares held.