Thought this might help anyone that uses lots of these. (sorry if this shows up twice. i thought i hit submit but didnt see it show up, so I reposted to be sure :P )
Alfalfa sprouts contain approximately 1.5% canavanine, a substance which, when fed to monkeys, causes a severe lupus erythematosus-like syndrome. (In humans, lupus is an autoimmune disease.) Canavanine is an analog for the amino acid arginine, and takes its place when incorporated into proteins. However, alfalfa that is cooked by autoclaving (i.e., subjected to pressure-cooking) doesn't induce this effect [Malinow 1982, Malinow 1984].
(Note here that the monkeys were fed semi-purified diets, with a canavanine content of 1-2%, versus a typical canavanine content of 1.5% (dry weight--that is, when completely dehydrated) for alfalfa sprouts [Malinow 1982]. )
Thus, although it would be very difficult for a human to eat enough fresh alfalfa sprouts to ingest even 1% canavanine, individuals should be aware of the potential risks, and consume (or not consume) alfalfa sprouts accordingly. (In particular, those rawists who juice sprouts should probably strictly limit or avoid the consumption of alfalfa sprout juice, due to the concentration effect that results from juicing.)