I guess I should blame my parents for giving me a Chinese name that sounds or looks like nothing short of being "Mr. Yu."
There are two people in my family who are truly Mr. Yu, my father and my brother. If you want to play safe, call someone "Hu Lao Shi," and it will never go wrong. In English, it's a lot safer to call someone Dr. Hu than Mr. Hu, especially if this person Blogs on the SciNet.