err, CAPM does not take into account inflation..
sorry my post isnt very clear, my point was that inflation erodses the value of everything and hence you should look at nominal returns alone, what capm does.
Also, inflation may erode the value of everything but the problem is that a savings account pays a fixed interest rate whereas other assets (e.g. property, food etc.) can increase in value over and above the inflation rate, leaving your savings account investment far worse off than the value of the rest of things. If you are investing in something that offers a return under the inflation rate you are losing money. It may not matter when you want to buy other things that have had their prices rise at rates under the inflation, but it will if their prices have risen at, or above, inflation rates (which is very likely!).
Inflation again is irrelevant. See CAPM.
Property and food is more volatile than cash. Not comparable in risk.