Me and my girlfriend have iPhones & iPads (well technically I dont have an iPhone yet), that would be 4 devices. We bought the devices at the same time so the chances of picture names overlapping is preety high.

I use Windows and my girlfriend too, and when we have to download files from our devices into our folder structures (which we share on the network) then some overwrite could occur if we are not really paying enough attention at the Overwrite? question.

Apple seems to use the same IMG_xxx.JPG / MOV for all pictures and videos (where XXX is an automatically increased by one number). I didnt find a way to actually change this prefix for whatever I want for example: ITCP_iPAD_XXX.JPG/MOV.

Benefits of having this:

1) By specifiying a specific and personalized prefix we could totally avoid the overwriting problem.

2) We could also quickly identify who took the picture without having to look at the details of the file itself and by just seeing the file name.

It would be really nice to see this from Apple, its a detail improvement that would make things easy for a lot of people, like us. 
This post has already been reported by me into Apple Discussions forums to increase the chances of someone taking care of it.