Why shouldn’t we be allowed to have multiple files with the same name in one directory, so long as they’re all different versions of the same file?
To wit:
$ ls -al
-rw-r--r-- 1 ardekantur staff 60 Jul 6 23:20 hello_world.c
-rw------- 1 ardekantur staff 62 Jul 5 13:00 hello_world.c
-rw-r--r-- 1 ardekantur staff 61 Jul 7 00:35 hello_world.c

One Comment
Vista kinda does that… macs with time machine sort of approximate the same thing as well. Of course, they don’t actually keep the files in the same directory with the same name - Vista renames them by appending a date, and I don’t know what macs do. But through some UI magic it appears to a user that past versions are there next to the current one, so it comes out about the same. It’s probably slightly less confusing to users to see it presented that way, and at least you know that all of your programs are only using the version you have marked as the “current” one.
Still, it’s a very cool feature. It’s one of the few things I like better about Vista over XP.