Bruce,

Typically I would recommend to form an LLC for the type of business you run. With LLC you can pretty much get all the advantages of Corporation without most of the disadvantages.

You would need a Corporation in some rare cases, such as is your company is filing for IPO. However, even in that case you could start with LLC and incorporate later (see our answer to the question Social networking website incorporating in CA)

Also, if you plan to reach out to venture capitalists they might require you to form a corporation (for no better reason other than thats how they were doing their business for decades), in this case you would just form a new corporation and dissolve the LLC, or just use your LLC as the shareholder in the newly formed corporation. Bottom line is, there are many right solutions to this situation.

Finally, the choice of state: you could either form LLC in Missouri since thats where you live and that has its own advantages, or form the LLC in one of the incorporation-friendlier states such as Wyoming or Delaware (however that goes beyond the scope of this question).

I hope that answer helps.