Not necessarily incompatible positions. It's perfectly possible you might want 16gb today but 32/64/etc. later down the line. In fact, based on apple's ram pric

Not necessarily incompatible positions. It's perfectly possible you might want 16gb today but 32/64/etc. later down the line. In fact, based on apple's ram prices, this is the advisable approach, providing you can get a machine which actually CAN have the ram upgraded.