Biting the hands that fed you…
Interesting quote by Bradley Horowitz in a Forbes article:
Google “crawled up on our backs,” says Horowitz. Yahoo! helped give Google its legs by incorporating the search engine into its portal. “About two and a half years ago, we realized we made a mistake” by not recognizing the value of the search market sooner. So Yahoo! “bought up all of the remaining relevant companies” in the search market in order to catch up.
I feel that Google “bit the hand that fed them”. Yahoo helped them a lot, gave them funding, used them as backend for yahoo search and featured their logo strongly (a big mistake in retrospect); and gave them the traffic that allowed them to grow their marketshare and fine-tune their search algorithms. Then after all this help, Google comes and competes with Yahoo in every other product, and trys to hire Yahoo’s brightest brains.
Its like a parasite that feeds on top of a host but grows so much and wants to eat the whole host. However, the host now woke up, and it will fight back the evil parasite 
— amr