Firstly, I want to say that I have enjoyed many hours of entertainment with these Buckyballs. I even bought two more sets so I could make some real cool structures with them. Since when did all products have to be safe for humans to ingest? It seems to me like all household cleaners, motor oil, industrial lubricants, hell ... even integrated circuits would have to be yanked off the market now.
All of that being said, I'm actually surprised no-one else has mentioned a particularly troublesome issue with bucky-balls that poses for even intelligent adults: peeling metal. After having fumbled with these bucky-balls for a long time, tiny slivers of metal have been peeling off, which would be fine if they didn't end up on my fingers. Just imagine a wooden splinter, only way smaller and more rigid. I've found them to be impossible to remove deliberately. Basically you have to go several hours, sometimes even a day or two, with the shavings on your finger and eventually they will fall off (either by being washed off or just falling off after awhile). Fortunately, I've been careful not to ingest the slivers or scratch my eyes but after having the slivers end up in my fingers a few times I've stuffed the bucky balls into a box and tossed them aside.
That doesn't mean I'm going to go complaining to the company about it like a cry-baby. I do realize that rare-earth magnets are quite brittle and they must be treated with care (which I thought I did -- but apparently not enough so). Perhaps I'll pick up some gardening gloves and give the bucky-balls another go.