Your argument, sir, is invalid!
"You should be able to post the packs because servers should be better prepared to stop them".
I call shenanigans!
Now that Notch has given modding the "go ahead" I wouldn't say it's hacking to decompile the .jar, though if you do that's fair enough. Regardless; writing a mod to add a massive death machine that kills everyone periodically is still better than an x-ray pack, because it doesn't give any one player an unfair advantage and then ruin it for all the other players without said advantage.
~Karenthian~