When we were in New York, my husband kept going on about these Buckyball things that he wanted. They are tiny little round magnets in a 6x6x6 block that you can make into various shapes. He wanted them to absent mindedly play with while he's on his very many work phone calls.
I bought him some for Christmas. He had a couple of days of playing with them, I got used to the familiar click of the magnets attaching to each other. He made them into a long line. Then he tried to pick them up and that's when all the trouble started. Some fell off the bottom. We heard them roll along our wooden floor and then *ping* as they attached to the nearest thing that was metal. We spent hours searching for the ones that were missing. We found some attached to the table leg. A couple had managed to work their way into the top of the radiator, I have no idea how. A few days later he was playing with them again and the same thing happened. It took us a week to discover them lying under the Christmas tree.
When you purchase Buckyballs, there is the option to buy extra balls. Do it. It only took us 3 days to lose some. And if it is at all possible to use them on a carpeted area, do that. Better still, take them to work. Or buy the Buckycubes so there's less chance of them rolling all over the floor. If you have children, don't buy them.
They are lovely fun, but we've had a couple of little Christmas tantrums because we are still missing a couple and we have no idea where they could have possibly gone since they aren't in any of the obvious places!