For some programs (rm isn't one of them), removing the write permission is sufficient to get an interactive prompt when you try to overwrite/truncate/delete the file.
I really like OSX's current metaphor, where files that haven't been touched in a while get "locked", and must then be "unlocked" to modify them further. Phrasing it in terms of stability rather than permission makes a lot of sense to me. It's too bad the metaphor isn't echoed in the CLI.
$ touch foo
$ chmod -w foo
$ rm foo
rm: remove write-protected regular empty file ‘foo’?
$ sudo chattr +i foo
$ rm foo
rm: remove write-protected regular empty file ‘foo’? y
rm: cannot remove ‘foo’: Operation not permittedIf I'm tapping a file that's been sitting there since the OS was installed and hasn't been touched since... Probably fair to ask me to confirm!