Central banks buying US stocks

I received a number of emails regarding central banks buying US stocks.
Some are freaked out by it but I don't understand why.
Since when where the central banks only limited to buying bonds,gold and foreign currencies.
Central banks are cash cows for the countries governments no matter how you put it .
Sure there their to make sure the financial structure is sound but whats next.

Lets put the acid of yourselves, If you had $2 billion to spend, what would you buy.
We are talking here for a year or 2 investment, risk free..
Remember the risk free that's the icing on the cake.

Debt from Europe ?
Metals at there current prices?
US Debt?
Which Currency is sound and cheap?
Which stock markets are safe and have potential to gain, and liquid?

So now that we are starting to see whats out there the options are seriously limited.
Yes they are going to buy Apple and GOOGLE so this is just going to increase the potential move in the US  stock market and get this?
Its basically fully backed by the Fed with a drop would trigger QE3 and 4...

The Germans nor the British will back there stock markets where as the US will and twice on Sunday as the saying goes...

cheers