True. That's why I said it keeps them "looking like" they are innovating. Failed or not, each small product or feature release gives them PR points. Look at +1, buzz or any other new products. They are all the rage when they are released. Everybody hails Google as the new king of innovation and when the products are killed a few months/years dows the line, the only people complaining are developers who took dependency on that product thinking it was a good long term platform bet.
lately, most of google's products have come out behind the curve, lacking polish and functionality, and then fail to gain traction and get killed off.