I've heard stories about this since I was a teenager.

http://www.smithsonianmag.com/histor...1020-Weekender

or

http://tinyurl.com/18r

I even remember reading articles in the Memphis newspaper when I was in
my 20's about hospitals x-raying candy and apples for things like razor
blades and needles.

Apparently no one has actually done this, except for one guy trying to
collect life insurance he'd taken out on his son to pay off debts. In
order to get the payout he had to poison a few other kids in the
process. He didn't get away with it.

Jill