A modern photocopier is basically a computer with a scanner and
printer attached. This computer has a hard drive, and scans of
images are regularly stored on that drive. This means that when a
photocopier is thrown away, that hard drive is filled with pages
that the machine copied over its lifetime. As you might expect,
some of those pages will contain sensitive information.
Some of the reader discussion veers into one or two only-semi-related,
but interesting areas. For example, did you know that Xerox invented an
image-compression technique (JBIG2) for its photocopiers that would
actually introduce typos into documents?