Most of my international travel is business related, and I have never once been asked more than a couple of questions, such as: "what countries did you visit?" or "what line of business are you in?" by the immigration officer. Most customs officers just ask me: "this is all of your bags?" (I travel light).

I don't think business or pleasure makes a bit of difference. I think it's more about the reaction to the questions that they ask (nervous, sweating, evasive, etc.).