Beware - you must think ahead when moving these magnets.Link (via Sensible Erection)
If carrying one into another room, carefully plan the route you will be taking. Computers & monitors will be affected in an entire room. Loose metallic objects and other magnets may become airborne and fly considerable distances - and at great speed - to attach themselves to this magnet. If you get caught in between the two, you can get injured.
Two of these magnets close together can create an almost unbelievable magnetic field that can be very dangerous. Of all the unique items we offer for sale, we consider these two items the most dangerous of all. Our normal packing & shipping personnel refuse to package these magnets - our engineers have to do it. This is no joke and we cannot stress it strongly enough - that you must be extremely careful - and know what you're doing with these magnets. Take Note: Two of the 3" x 1" disc magnets can very easily break your arm if they get out of control.
Mark Frauenfelder is the founder of Boing Boing and the editor-in-chief of MAKE and Cool Tools. Twitter: @frauenfelder. His new book is Maker Dad: Lunch Box Guitars, Antigravity Jars, and 22 Other Incredibly Cool Father-Daughter DIY Projects