Beside the copyright issue, what kind of risks I need to notice on making a web apps(eg. fb apps)

I'm developing a facebook game, at the very beginning, my will is trying to launch the game asap, after a month coding, I finish 70% coding of my game, and the rest part are images, then 2 of my friend join in because they are interest, they suggest that we form a company together, me 60%, 40% is them, however, I think that it is not necessary to form a company at this moment, I plan if any success is forecast after 1 month of launching, then it would be nice to form a company rather then start at the very beginning.

But another problem is I don't know are there any trap or risk I need to notice if I do not form a company. Will it be difficult to migrate the new company details later, or anythings I will lose if I do not own a company, please help, thanks.

I agree, start with the product, then worry about the business later. When you start putting money into the business, or borrowing money for the business, or start getting revenue coming into the business - that's a good time to worry about your business status for tax purposes.

If you are a sole proprietorship you can file taxes on a Schedule C. If you are going to have partners you'll need to set up a LLC or a S-Corp.

Running a sole proprietorship on a Schedule C and checkbook is easy. Dealing with partners and an LLC or S-Corp is much more complicated. Don't give away ownership and add partners without serious consideration, and only if those partners are contributing real money or significant labor and/or expertise.

Good luck.