Did you know that SMS texts are sent as plain text between phones and stored enroute by by mobile carriers? This enables your SMS texts to be trvially intercepted and read by staff at those companies and the government without your consent or knowledge.
Fortunately there's an elegant tool for encrypting SMS texts: Text Secure
TextSecure gracefully recognises contacts who have TextSecure and those who don't, enabling you to continue to texting secure in the knowledge that the spooks can't see what food you've been asked to pick up on the way home or how lame your come-ons are to that someone special in your life.
I encourage you to encrypt your SMS texts by default to assert your right to privacy. Third parties have no right to view your communications and you can assert your right to privacy by encrypting communication by default.
Note: This is only avilable for Android. If you use an iPhone you're screwed, Apple owns you, keeps your data and feeds it to national security agencies. Sorry.