This is surprising, I guess having it has an IE default really has more of an impact then I expected. I wonder how much the amazon gift card thing helped as well.
Not really. Before Bing had 20%, Yahoo had 20%. Now Yahoo search is powered by Bing. MS pretty much bought the marketshare with the Yahoo deal and Yahoo was happy to have someone else do the heavy lifting on search. I believe Yahoo search is also the default on Firefox now.
IE defaults can only take you so far.