When did using cold water pipe for outlet grounding become a no-no?

[sparkycoog]

I've never done this, but have seen it done before so I'm curious if running a grounding wire to a cold water pipe to convert a 2 prong outlet into a grounded 3 prong outlet was ever allowed by the code and if so, which year that was (just so I can sound smart and important with other electricians).

Also, while on the subject, I know if you're going to run a grounding wire to the panel, you might as well run a 12/2 and update the whole circuit, but for argument's sake, would you be allowed to run a 12 awg green THHN wire from one receptacle through the walls and attic back to the panel, assuming of course that it would only stay in that branch circuit and not mixed with others or would it need to be protected with conduit or flex? Again, just for general knowledge and I wouldn't do this myself (though again, I've seen it).

 

[infinity]

From another active thread:

Under the 1990 NEC {250-50(b)Exception} and in earlier code cycles a bonding jumper was permitted to be run from the grounding terminal of the receptacle to any water pipe that was bonded in accordance with 250-80(a).

250-80(a) Metal Water Piping. The interior metal water piping system shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor where of sufficient size, or to the one or more grounding electrodes used.

http://forums.mikeholt.com/showthread.php?t=164686