After Apple has openly admitted signal problems with first iPhone 4 almost every other manufacturing brand announced that this has never happened to their phones. Recently after this, Apple uploaded a video online of many other smart phones losing signal if held in a certain way.
A video posted by AdvancedSafetyDevice shows a deadly grip for HTC HD7 which causes loss of signal to smart phone. You may argue that two inches displacement could be a factor but I disagree. Here, take a look for yourself: