Well, I don't think I'd really call these people "bad parents" either but it was certainly a mistake that happened and it really should not have, after having the child for three years and she's about the age where she's really walking, wanting to learn things, and getting into things I would think stuff with small pieces like that would've been placed in high positions long ago.
Granted, I've no kids but I've watched my mom babysit a number of kids over the years of running her business as well as witnessed friends and family members have and raise kids. One thing that always seemed pretty common was that pretty much as soon as the kid is able to roll over and somewhat mobile you lock down anything and everything possible. Tiny stuff stays well out of reach, doors and cabinets get those frustrating locks/straps put on them, gates go up to preclude where the child can go, plugs on the outlets, etc.
Mistakes and shit can happen, sure, just strikes me as odd that this toy would've been anywhere near a place where the child could possibly get to it.
Anyway, I'm glad the child survived but it's frightening to read what happened here could have been fatal (I'm guessing that the magnets have some sort of heavy metal in them that wouldn't be good to digest) hell it's probably a small miracle the child didn't choke on the magnets when she was trying to consume them.
Again, thoughts to the family and glad the kid survived relatively unharmed from the experience.
Choking wouldn't have been likely. Remember that candy "Sixlets". Those are what bucky ball magnets look like, just without the delicious candy part.
Bucky ball sphere magnets: http://www.thinkgeek.com/geektoys/science/bbe8/