I am thinking that in the past, if you did do this, it would destroy a drive. I'm talking really ancient hard drives who, when they lost power would cause a head crash.
That has been solved by the hard drive manufacturers, so that you wouldn't loose so many hard drives due to a power outtage.
What I am saying is that what you are doing most likely is using the emergency features of a hard drive. If some cables fall out of the drive for who-knows-what reason, do you want a totally dead drive from that? Most likely the drive has emergency procedures to handle situations like this. I still wouldn't throw my drive into those procedures because I was too lazy to shut down my machine.
If you really need a hot-swappable hard drive, get a hard drive enclosure that has firewire/usb 2.0 connections on the back. That was designed (as far as I know) to hot swap.
Anywho, as the old saying goes, you were told that doing that was bad, so if it breaks when you do it, you can only be held responsible. If you do try it, good luck!