Don't use magnets anywhere near computer stuff. The hardward can be completely lost because it has tiny bits of metal in it. I put a magnetic business card on the side of a metal CPU case. It took one weekend to completely erase my computers programs. Not good. Pins that have been on a magnetic pin cushion have usually developed some amount of magnetic properties. Done use pins from a magnetic pin cushion in your machine sewing. I finally threw my magnetic pin cushion away and purchased a magnet with low pull to help pick up pins on the floor. Then I transfer them to my regular pin cushion.
Another hint: You can take a magnetic strip usually used to make refrigerater magnets. Put a long strip on the front of those floor cleaners. It makes it easy to sweep up the pins.