One of the more interesting and surprising feedbacks that I got from my presentation on .NET Worst Practices at the .NET Deep Dive developer event was how many experienced .NET developers didn't realize the significance of the difference between "throw" and "throw ex" (both in C# and VB). I thought that I would explain and show it here, but one of the conference attendees (and an XML MVP) already did it forme on his blog - so check out Oleg's entry that summarizes my explanation of this issue. He also includes a comparison to the Throw keyword in Java.