Ford announced Monday that its Hertz car rental group filed for an initial public offering. The offering is estimated to be about $100 million, but the actual IPO could be worth more or less. Hertz is the world's largest general use car rental operation and has been a part of Ford since 1994. Ford could ultimately loose a major buyer of its cars. In the past, Hertz has been a convenient place to offload the aging Taurus and Sable models. Thankfully, the Fusion and Five Hundred and their cousins look more promising.