Without the slash, an empty variable would result in a command line of "rf -rf" which would simply fail due to the missing argument.
There is absolutely no need for having a trailing slash, it's not as if "rf -rf foo" and "rm -rf foo/" can ever mean two different things, there can be only one "foo" in the file system after all.
Very interesting way of introducing an epic fail with a single character, that really looks harmless.
That's true, but the original code was akin "rm -rf foo/*" and that's different, since it removes the content of the directory while preserving it.
This behavior is especially common with regards to URLs; there are many flamewars about whether URLs “need” a trailing slash or not.
I don't understand how anyone works in the very unforgiving-of-accidental-delete *nix world without those aliases.
The useless confirmations on every deletion is so intrusive that people will instinctively try to work around it. In the best case they'll undefine those crappy aliases in their own shell config, or maybe gravitate toward writing /bin/rm rather than rm to avoid the alias expansion. In the bad case they'll learn that "rm -f" will override "rm -i", and get in the habit of using that to shut rm up. Too bad that "-f" does more than negate "-i"...
People who don't actively work to circumvent the braindamage will almost certainly end up reflexively teaching themselves to just answer "y" to the prompts without reading. Or worse, they'll learn to depend on the prompts being there, and doing "rm * " when their intent is not to remove everything. "Yeah, I'll just answer 'n' for the files I want to keep". That's going to be a really nasty surprise when they use a machine without that alias.
No. Just no. Don't do it.
The solution in zsh is much better. Warn for "rm * " (or "rm * .o", etc) no matter what, since that's both very dangerous and very rare. But don't waste the user's attention on every single deletion.
Perhaps I should have said "sane systems" ;)
Fedora ships with that alias by default FWIW.
It has the added benefit of being inside the "RHEL/CentOS" ecosystem (similar commands, structure, etc), provides a glimpse of what's-to-come in future releases of RHEL/CentOS, and since majority of servers in the enterprise are RHEL/CentOS based, it's a natural fit.
All that aside -- have you tried Fedora 21? It's a complete overhaul from previous Fedora releases and has a lot to like and offer.
I'm sure it works for some but it's not for me.
… I don't think anyone does that.