Magnets and magnetic media (floppy and hard disks) don't get along well. Magnets seem to be all over electronics these days. The docks for my Motorola phone use magnets to determine let the phone sense if it's in a car or desktop dock. Many of the cases have magnetic flaps. I've not encountered any problems using any of these, including with a uSD card.
I was leery at first, but I'm comfortable using magnets around Android devices now.
NOOK devices use flash storage, not magnetic, so there is very little a magnet could do that will hurt the device.
I've seen more than one review that claims the magnet in the strap actually damaged their nook or other devices.
Are these people just making incorrect assumptions when something else is to blame, or is there something to their claims?
I know magnets and electronics are not the best of friends.
Magnetism is used as an integral part of many electronic components:
- High-fidelity audio speakers (the tiny ones in some electronic devices are often not magnetic, but piezo-electric: http://en.wikipedia.org/wiki/Piezoelectricity ).
- Magnets are used hard disk drive motors, and in "stepper-motors".
- Magnets are sometimes used in "relays" in some devices (eg, for turning power on or off).
- Powerful magnets are used in most CRTs (eg,, older televisions and other video display equipment).
- Magnetic materials are used in many physical recording media (eg, hard and floppy disk recording media, recording tape, etc).
Except for the last two, the use of magnets around electronic components should not pose a problem. When floppy disk media were in common use, I used to ban all magnets (eg, the refrigerator ones) from my house, to avoid accidental erasure. Even now, I like to limit my usage, as magnets (especially strong ones) can magnetize other ferrous materials that they come in contact with: Eg, a magentized screwdriver, useful for picking up and holding small screws, can magnetize the screws.
As noted above, magnets are an integral part of most CRTs. The magnet (along with additional magnetic fields generated by circuitry) are used to deflect the electron beam in a CRT, and as a result, a magnet placed near a CRT screen will temporarily deflect the beam and distort the image. In addition, if such a magnet magnetizes (even to a very tiny degree) the metallic screen inside the CRT, the image distortion may be permanent.
The magnets in the B&N covers are weak, and the biggest risk is setting a floppy disk on top of one of the covers.
All that having been said, I have two B&N "Lautner" covers with embedded magnets. While I would prefer covers with no magnets, all the other covers I have seen have other minor deficiencies.