Because, in many cases, it will void your warranty, and if you get caught by Microsoft, your console (but not your account) will be banned from Xbox LIVE.
that's why it sucks my cousin got banned like that too so is my brother's too what the hell. This Xbox 360 can suck my penis
Modding your 360 does not affect anything in a negative manner. Your original discs will work the same as they did before. -Personal experience from modding XBOX 360 for 3 years.
NOOBS
Yes especially online modding.
I wouldn't want to know because you can get a suspension from modding on Xbox LIVE
Modding is illegal on the Xbox 360 and therefore you will get banned.
Modding affects the console.
You can do it by modding your xbox 360. But it is very dangerous as virus can be transmitted through it.
Yes if not done right.
It gives you a console suspension from the Xbox LIVE Service. Where you Xbox 360 console will be usless where it cant be used anymore.
Modding is illegal.
Modding is illegal and you will get banned from Xbox permanently if caught.
There are many sites which provide you with information about modding a xbox 360, however, this is very illegal and should not be attempted.