I always recommend, if you can, to patent or protect whatever your idea is. If you can't, you have to make your best judgment. Sometimes people don't get anywhere because they sit on something, so afraid to reveal it. And yet, in the reverse, sometimes if you expose something too widely, you can risk losing it.
It almost goes without saying that when you are a startup, one of the first things you do is you start setting aside money to defend yourself from patent lawsuits, because any successful company, even moderately successful, is going to get hit by a patent lawsuit from someone who's just trying to look for a payout.