sikdmax - Got any references? I've not heard of it happening IRL, it just seems like a danger to me. (Can the feds subpoena something the state promises by law to keep private, anyway?)
Quoting the relevant laws to back up what I said:
SB420:
HSC 11362.7
(h) "Serious medical condition" means all of the following medical conditions:
(9) Persistent muscle spasms, including, but not limited to, spasms associated with multiple sclerosis.
I got written in, no need to prove that it's effective or necessary for my condition 
11362.71 (f) It shall not be necessary for a person to obtain an identification card in order to claim the protections of Section 11362.5.
It is OPTIONAL
11362.765. (a) Subject to the requirements of this article, the individuals specified in subdivision (b) shall not be subject, on that sole basis, to criminal liability under Section 11357, 11358, 11359, 11360, 11366, 11366.5, or 11570.
If you're registered, than you're OK for: possession; cultivation; possession w/ intent to sell; transport/give away; location for selling; storage; storage again
11362.5 (d) Section 11357, relating to the possession of marijuana, and Section 11358, relating to the cultivation of marijuana, shall not apply to a patient, or to a patient's primary caregiver, who possesses or cultivates marijuana for the personal medical purposes of the patient upon the written or oral recommendation or approval of a physician.
... if you're doing it just under the proposition - i.e. no card - then you only need the ORAL recommendation of A physician. Doesn't say it has to be YOUR physician even. However, then it's only good for possession & cultivation.
11362.77. (a) A qualified patient or primary caregiver may possess no more than eight ounces of dried marijuana per qualified patient. In addition, a qualified patient or primary caregiver may also maintain no more than six mature or 12 immature marijuana plants per qualified patient.
(b) If a qualified patient or primary caregiver has a doctor's recommendation that this quantity does not meet the qualified patient' s medical needs, the qualified patient or primary caregiver may possess an amount of marijuana consistent with the patient's needs.
OK for up to 8oz / 6 full plants by default. Unless your doctor says otherwise, in which case however much they say you need, is OK.
8oz is a LOT. I would bet the cops here have busted people as 'possession with intent to distribute' just based on having more than 2oz. But the law says it's cool. 
11362.79. Nothing in this article shall authorize a qualified patient or person with an identification card to engage in the smoking of medical marijuana under any of the following circumstances:
(a) In any place where smoking is prohibited by law.
(b) In or within 1,000 feet of the grounds of a school, recreation center, or youth center, unless the medical use occurs within a residence.
(c) On a schoolbus.
(d) While in a motor vehicle that is being operated.
(e) While operating a boat.
No smoking while driving.
11362.81. (a) A person specified in subdivision (b) shall be subject to the following penalties:
(1) For the first offense, imprisonment in the county jail for no more than six months or a fine not to exceed one thousand dollars ($1,000), or both.
(2) For a second or subsequent offense, imprisonment in the county jail for no more than one year, or a fine not to exceed one thousand dollars ($1,000), or both.
(b) Subdivision (a) applies to any of the following:
(4) A person who breaches the confidentiality requirements of this article to information provided to, or contained in the records of, the department or of a county health department or the county's designee pertaining to an identification card program.
Giving info to the feds is a misdmeanor
)
