If you haven't heard yet, Microsoft and Yahoo! have inked a 10 year deal to partner on search and advertising. You can learn more about the details of the deal, which I won't go into here. If the deal is approved by regulators, we could see changes in Yahoo and Bing search and advertising early next year, from the sound of it.
I am a pretty loyal Googler. Google hasn't really failed me yet for search, and I am familiar with it, so I use it -- one could say -- religiously. After the launch of Bing, I did some vanity Binging -- I "binged" myself, I admit it! And was satisfied to discover that I owned "Gregory Heller" on Bing for basically the first 5 pages. I Binged a few other things, and then next day went back to using Google. Bing is responsible for less than 5% (closer to around 2%) of search traffic on many of the sites I track stats for. Google accounts for 90% or greater of the organic search traffic, so I "go where the people are." It is worth noting that these numbers do not jive with Comscore's latest traffic numbers (from June) that show Google with 65% of search, Yahoo! with 20% and Microsoft with 8%. So Yahoo! and Microsoft could soon account for a combined 30% of search.
But now that Bing will power Yahoo! search, these numbers will increase, and as Bing improves with the access to Yahoo!'s search data, the number of people using Bing will probably increase. I've also noticed an interesting blip in the stats recently, Bingers view more pages, stay longer and have a lower bounce rate than googlers. This is born out in some of the coverage I've read about Bing, though as Rand Fishkin (of SEOMOZ) allows in his post on the deal, it is unclear if this is due to demographics of Bingers or the better presentation of Bing search results (with more context).
Nonprofit organizations and Non Government Organizations that rely on organic search traffic must now begin to serious consider Bing. What does that mean? Get a Bingmaster account (I'm coining that term, Bing Calls it "Webmaster Tools" which is the same as what Google calls it) and start analyzing your traffic from Bing. Try out your keyword searches in Bing and Google and see how your site turns up (and who else turns up). And of course, pay attention to new developments with Bing and Yahoo! of which there are sure to be many over the coming months, especially if/when regulators approve the 10 Year deal.