"Data expands to fill
the space available for storage"; buying more memory encourages
the use of more memory-intensive techniques. It has been observed
since the mid-1980s that the memory usage of evolving systems tends
to double roughly once every 18 months. Fortunately, memory
density available for constant dollars also tends to about double
once every 18 months (see Moore's Law); unfortunately, the
laws of physics guarantee that the latter cannot continue
indefinitely.
