Apple earned only 1.1% on its cash

I found this article about Apple interesting.

They found this bit in Apples earnings report:

"The weighted-average interest rate earned by [Apple] on its cash, cash equivalents and marketable securities decreased to 1.11% in the third quarter of 2009 from 2.66% in the third quarter of 2008."

So Apple only earned 1.11% interest on their money. Yet they have $24 billion in cash!

I wonder if there is some reason for such a low return. I would assume they wouldn't have 100% of their cash in low interest baring accounts like simple money markets. With that much money they should be able to diversify into various kinds of bonds at a minimum. Its possible they've made some poor investments and the low return reflects them losing some value. But shouldn't a company like Apple be investing in itself? They should be buying facilities and investing in new income generating projects instead of sitting on a giant pile of cash that they get relatively little return on. Even if they don't have good opportunities to use their money with their own business then you'd think they should do a better job of managing the investment of their assets.