I have to say I’m shocked by this news, especially considering that Bing will be behind Yahoo’s primary search engine here in the states and in Europe.
Bing seems to lack mobile search. While there search page is optimized for mobile, they don't seem to rank mobile differently. That alone could be a deal killer for the Japanese market.
Yahoo Japan is very much a separate entity from Yahoo.com.
For instance, they're still operating geocities.jp, whereas the .com (and all the others) has closed, and in general they seem to be able to make a go of things where the .com version falters.
Also there's some bullcrap at the end. Most of the time in yahoo history the "heart" of it was done by a 3rd party company,e.g. google. Which became a company we know only after yahoo used them as their search engine long ago
Bing seems to lack mobile search. While there search page is optimized for mobile, they don't seem to rank mobile differently. That alone could be a deal killer for the Japanese market.