Yesterday (Sunday, April 26, 2009) the FDA issued a statement warning about possible salmonella contamination in alfalfa sprouts and sprout blends containing alfalfa sprouts.
Because they're in a mid-growth stage, sprouts can harbor e-coli and all sorts of other nasty things inside the seed-end that is impossible to wash away. Pregnant women should never consume raw sprouts of any kind because of this and, especially now, everyone should avoid commercially-grown alfalfa sprouts until we get the all-clear from the FDA.
This isn't the first commercially-grown salmonella outbreak in sprouts. Personally, I avoid these little buggers altogether.
Image courtesy of pternz at photobucket.