With U.S. corporations sitting on some $1.8 trillion in cash and unwilling to invest in new products or personnel, it was only a matter of time before we saw a wave of merger and acquisition activity. Today, Warren Buffett’s Berkshire Hathaway said it would participate in a $23 billion purchase of H.J. Heinz. In an $11 billion deal, American Airlines and US Airways recently merged to form the world’s largest purveyor of lost luggage. Dell agreed to a $18 billion multi-party buyout. And Random House and Penguin are on the verge of forming the biggest book publisher in the world. With the U.S. economy in slow recovery and Europe’s debt crisis easing, more such deals are likely to follow.