When planning a website or any other company what stops your potential investors from stealing your ideas or design and just doing it on their own know that they now what it is?
I'm going to be blunt and say that nothing can stop them. Then I'll explain.... You can use a NDA or DNC... but those are only worth the money you are willing to spend to fight someone. I know there are a handful of lawyers on here that can offer you real legal advice on this so I'll be straight forward and say I'm not a lawyer and this is not legal advice.
From a business stand point too many people leave ideas on the shelf because they are scared that someone is going to steal it. The reality is that 10 or more people are about to start the same exact business you are thinking about. Unless you have found a cure for AIDS or you have designed a new techno-gadget then you really should worry less about people stealing your idea and more about making it a reality.