I've had several friends come to me after installing their first OS X application, saying they thought they had a virus. "Whenever I try to run this applicatio

I've had several friends come to me after installing their first OS X application, saying they thought they had a virus. "Whenever I try to run this application, I get the warning 'This was downloaded from the internet', etc., etc. I have to click 'Okay' every time I use the app. It doesn't seem safe." The problem? They had dragged the app straight from the disk image onto the dock. That said, OS X installation is about as simple as you can get. (Though I wish Apple would finally include Homebrew as its default package manager.)