It can be interesting to match the behavior of `rm` exactly like UNIX rm and alias `trash` as the place of `rm`. It's still hard to convince people to use a another command than `rm`. Specially if you can do almost the same thing by using `mv` and predefined directory.
Not really. The mv command isn't cross-platform and moving to trash is not just about moving the file to a "trash" directory. On all OSes you'll run into file conflicts. The user won't easily be able to restore the file. It won't work on an external drive. The trash directory location varies between Windows versions. For Linux there's a whole spec you need to follow. On OS X you'll loose the Put back feature.