Once they go online then all that 'hacking' is completely useless. A great example of this is XBOX-Live. Try taking a 'hacked' 360 onto Live and see how long it takes before your machine is banned. This is exactly what they can do with online D3. It isn't rocket science and knowing that Blizzard does want to keep the integrity of the game and community at it's highest, they have already baked this in.
If you are only going to play offline, I say hack away. The only person you are cheating out of the real fun experience is yourself.