I don't think you have too much to worry about in a laser printer, but
Vlad is defifinitely right about magnetic media. While is may actually
be possible for the degaussing to disturb the particles of toner, first
of all you wpuld have to already be printing whe you turn the monitor
on. Of course I'm talking the quality of one page, I don't think it'll
hurt the printer at all, and a laser printer might actually be better
off demagnetized. I really don't know, but it fits

Also realize this, monitor manufacturers don't want to waste a magnetic
field, they would rather keep it contained. It costs money to create
that field and not focusing it properly cost money in higher current
components and power drain. If you look at the DG coil in some monitors
you'll see it's arrainged in a figure eight, or more that one figure
eight. They want to "focus" that field on the tube, not on something
next to it.

JURB