I just happened to notice that one of our 15" MacBook Pro's running 10.5.6 didn't have the eject icon in the sidebar beside ejectable drives like a USB flash drive or an external hard drive.
We have two other MacBook Pros and two Mac Pros and one PowerMac G5 and they all have the eject icon when you mount an ejectable drive. I didn't need to hover the name of the drive, like you, but it is a lot easier to just click the eject button instead of right-clicking to eject all the time.
I found another post that suggested:
Hello flag:
I suggest you trash that preference file and restart.
Barry
this was a suggestion to someone who had the eject icon in the sidebar, but when he/she clicked it, nothing happened...
I'm going to give it a try tomorrow.
By the way, I would have liked to have included an image in this reply, but I don't see a way of importing an image into the reply window, nor can I drag and drop an image. (eg. a simple screen shot.) any ideas?