I know this is old news, but eBay took the kid gloves off last week by pulling their SEM dollars from their Google channel. Timing was such that it coincided with eBay Live, and Google's attempt to hold a "freedom of choice" party to encourage the eBay community to push eBay to support Google Checkout.
Now, I don't disagree that the timing had to do with Google's antics; however, companies as big as eBay don't just pull their SEM spend without having some good data to suggest that you aren't going to lose out on the deal. Something tells me that eBay is questioning their strategy on keyword bidding (and I've been right about eBay before :) ). This is something I haven't seen talked about in the blogosphere. Google is an impressive company with an impressive track record. But just like IBM, Microsoft, HP, Dell, and a plethora of other companies, they are assailable. Everyone is (Steve Jobs, are you listening?). However, the real insight here is: is SEM spend on Google really worth it? eBay is challenging that notion. What if they are right? SEM spend won't go away, but it will mean that SEM customers will spend less and less for keywords (I've learned firsthand that many small businesses find keyword bidding too expense and generate a negative ROI) in the e-commerce space.
I am looking forward to the next year in this space. I predict this is the first chip in Google's armor, and they will need to figure out a way to address (Google Analytics is a good way to counter... show customers their ROI in a measurable way) if they want their stock to keep climbing.