You might take a look at my page on Understanding Virtual Memory and Activity Monitor. A much better indicator of whether or not additional RAM is needed is found in the number of page outs. A page out indicates an 8KB page of memory has been removed from RAM and written to the Swapfile(s).

Based on my experience with Microsoft I am inclined to believe internal pointers within the application are more likely to cause a file to crash or become suddenly unusable than the amount of RAM in your system. However, insufficient RAM, can force premature paging out of data to the swapfile(s) and corresponding paging in of the same data when it is again needed will very definitely cause system performance issues and sluggish application functioning.

If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein