Do you also sign any NDA or anything that would protect your client's "IP"? What if a client had a great idea, shares it with you, you say "NO" and then [conve

Do you also sign any NDA or anything that would protect your client's "IP"? What if a client had a great idea, shares it with you, you say "NO" and then [conveniently] after a short while, the same idea is seen implemented elsewhere? I'm sure you are not into such things seeing what some people have to say about you, but I'm just curious how you go about protecting your clients' "ideas".