Found this interesting post on Sriram Krishnan's blog where he describes the origin of the Vickrey auction that is used by Google and Yahoo! for the online advertising. Very interestingly, although it has some side-benefits of removing winner's curse and bid shading (see links on Sriram's blog), the real reason why this process was adopted [instead of the traditional English auction] is that the Google systems people wanted to reduce the loads on the server that would have resulted from people changing their bids rapidly:
There have been several articles documenting the work of Google's Salar Kamangar and Eric Veach in bringing this to AdWords. What is lesser known (atleast to me )is that they implemented this model to solve another problem entirely. I came across this old talk from a Google employee - in the speaker notes, it talks about how Kamangar and Veach implemented this feature to stop advertisers from logging into the system and modifying their bids constantly (since that's what people tend to do in an open English auction). By implementing a second price auction, they were hoping to reduce the load on the system.