Given my situation, one might think that I would have more insight into the culture of Google vs the culture of Yahoo, but truth be told I really don't. Instead, here is an article from CNnet that talks about the differences between the two companies from a corporate culture point-of-view: Google vs. Yahoo: Clash of Cultures.
I can't comment on the Google side of things, but I don't think that the portrayal of the the Yahoo side is completely accurate. The technical and intellectual culture inside Yahoo is actually very vibrant although maybe not as much in the academic research form of way (although Yahoo! Research Labs might be different) .
The culture of Google and Yahoo IS different and the type of people each company attracts are different. The focus of the two company is also different but both companies are built on technology and it is the technology that keeps both company fresh and relevant.