Earlier quoted context omitted.
In case anyone wanted a real answer, it's just advertising, as it has always been: http://static.tumblr.com/7drgjla/386nnw4n9/yahoo_inc._2014_a... "We generate revenue principally from search and display advertising on Yahoo Properties and Affiliate sites, with the majority of our revenue coming from advertising on Yahoo Properties. Our margins on revenue from advertising on Yahoo Properties are higher than our margi…
The REAL answer is "a tax efficient proxy for holding Alibaba shares".
Matt Levine did quite a long writeup about this a while back: http://www.bloombergview.com/articles/2014-04-17/how-can-yah...
Taking an uncharitable view, Yahoo!'s core business actually has negative value -- and the current round of layoffs is a direct result of Wall Street pressure to stop subsidizing said core business and preserve the value of the Ali Baba stock.