I’ve often wondered how much invention never sees the light of day purely because of the enormous amount of time and money needed to defend patents from a world of vultures. It really is a shame that there isn’t an inexpensive way of defending your intellectual property, because the world could have so much to gain if there was.
Like others have mentioned, there’s a big risk that if its a worthwhile invention, then once the application is filed others will steal it.
So it could be advantageous keeping the concept out of the public domain, at least until your sure you can sell plenty in a short space of time to generate the cash you may need to defend your patent.
You can use nondisclosure agreements if there are potential clients you would like to pitch the concept at. Most honest traders are happy to sign them.
In patent law, you are allowed to make disclosures to potential clients to test an inventions market feasibility. The law recognizes that you are an inventor, but perhaps not a marketing genius. I think there is a window after a disclosure is made at which point a provisional specification should be filed. A bit of googling should throw a bit more light on that.
If there are legal matters you are uneasy about then an hour with a patent attorney would be a wise investment… you might as well get used to spending plenty of money anyway because new invention and burning cash have an intrinsic magnetic attraction.