In clear water situations, bass can see the swivel and may or may not shy away from your lure. That's the time when a swivel is a bad idea. And another thing, Bass Pros hardly ever use them. You can get a much more realistic action by tying a lure on the line directly. You should however use a swivel with crankbaits or spinnerbaits
There is a method of quick lure switching which is to tie a loop at the end of the line. You thread the line through the eye of the lure as if there is no loop, open up the loop, pull the lure through the loop, and tighten. This is an effective way to simulate a direct tie-on and be able to switch lures fairly quickly.
Another thing is, where you tie your swivel on makes a week spot in that piece of your line and you risk your line breaking with a medium to large bass. That's another good reason for using the loop.
I hope this is helpful. It sure has been very helpful to me in the past.
You can use the swivel during line retrieval and when preventing undesirable tangling. You can use it when using a spinning reel or a lure that pulls hard on the line. For more information about the fishing swivel, check on http://en.wikipedia.org/wiki/Fishing_swivel.