I personally think that IP protection paranoia with (for example) NDAs is overrated. Ideas are hard to protect because they're generally easy to come up with.
(I'm talking about web products here, scenarios will differ if you're doing something else).
Executing on an idea, however, gives you other things. Code (which can easily be protected with a license and NDAs), a brand (which is protected via trademark), a userbase (which is fickle, but you can work on making them happy and keeping them), a partner network (make it worth their while and they won't go anywhere), etc.
This gives you a Product.
Products are usually easy to clone (creating something that has the appearance of being technically equivalent), but hard to execute on (or in other words - turn it into a Product in itself).
Stop worrying about the source code leaking. Just assume that it has been leaked already. Unless you're sitting in a basement doing everything yourself, other people will have access to this code. If you out-source development to a third-party, the code has already been leaked.
What you should instead be worrying about is the security of your codebase. As you're obviously outsourcing, you should have a competent developer managing the outsourcing process and auditing the code for security flaws.
Bottom line : don't bother protecting the idea, use boilerplate NDAs and licenses for the code and its development and have strict auditing procedures for outsourced code development.
If you're starting up, IP really is the least of your concerns. Just assume everybody out there has illegal access to your source code, plan appropriately and stop worrying about it.
