I believe raw beans destroys important digestion enzymes.
Edit:
Okay, not that yahoo is all that scientific, this is the only source I've found that talks about why not to feed it to them.
http://answers.yahoo.com/question/in...AAguRq0&show=7
OTHER OFF LIMIT NEVER EVER FEED are
raw dry beans/Peanuts (contain anti-nutrients that destroy Vit. A & digestion enzymes, causes red blood cell clumping)
raw sweet potato
green bananas (inhibits digestion of starch)
green potato skin and eyes (contains a toxin)
wild insects
raw bulk tofu
mouldy Cheese
liquorice (suspicions of neurological poisoning)
raw red cabbage (contains anti-nutrients that destroys thiamin)
raw artichokes (inhibits digestion of protein)
raw olysters/clams
Edit again!:
Found the source
http://www.pxrats.com/diet2.html