Magic beans are a VERY useful freebie in this game..
When you open the game and your lives are full, ie. you have your maximum 5 lives, all the lives people have sent you will be beans, each life you were sent will be 100 beans.
Beans can be used to buy SHOVELS..
Beans can also be used to make defeating RANCID easier.
If you are getting short of magic beans simply send out requests for lives to all your friends as often as possible and you'll get them all back as beans when your lives are full.