Count me as another person that absolutely hates it when selections can be dragged with the mouse. For me it is totally counter-intuitive behavior and I have only succeeded in accidentally moving text with this "feature".
That said, everyone is different and I can imagine that this feature might be very intuitive and helpful for someone else. If this functionality is added, I would suggest using it along with a modifier key. So, for example, you could only drag a selection if you are holding down the ctrl key at the same time. Also, please add an option for people to be able to disable it.