Not an issue. Here's why. The electric motors in the machine also have magnetic fields bigger than a common magnet.
I have a question I hope someone can answer for me. It's not really about computers but computerized embroidery machines. For those of you that aren't familier with these they are basicly sewing computers. There are sewing/embroidery machines that have a hard drive, displays etc. You put material in a hoop and it embroiders. A third party manufactor has introduced a hoop that uses magnets to hold material in place that you wouldn't want hoop marks on that on certain fabric can't be removed. We are having a debate about whether the magnets are strong enough to be of any concern that if left close enough to the computer end of machine could damage it. IMHO it's just not worth ruining a $5,000 machine. The magnets as far as I can tell are about a nickel in circumference and about double the thickness, that hold fabric to a metal plate placed inside the hoop.