This sounds like a good idea. Keep your code secret, and nobody can hack it, right?
Well... it's not that easy. Code gets leaked all the time. Big chunks of Window's source code have been leaked, for example. If you rely on secrecy only, all it takes is one disgruntled employee to bring everything down.
Another problem is that hackers can analyze a program from the outside, and make good guesses about how it works. If you did something obscure, chances are that someone else did, too. All it takes is one clever hacker.
Keeping your code secret is fine, but don't rely on it.
Where referenced