Here are some other good resources I have found in addition to that NORML article which seem to corroborate the findings:

AskTheExpert

http://www.labcorpsolutions.com/imag...Flyer_3166.pdf (this one is a pdf file, you'll need adobe to read it)

Erowid Experience Vaults: Cannabis Urine Testing - THC Detection Times in Occasional Smoker - 37341

Erowid Cannabis Vault : Drug Tests (isn't erowid great?)

I think that generally there is a lot of misinformation out there when it comes to the question of "how long does it stay in your system." Most people come across some hearsay and treat it like fact when in reality there have been very few scientific studies done to test the validity of any argument.