Seems like they're giving people a reason to use their products, and then making a play to have an OAuth-level relationship with the users. Maybe they want visibility into how a user authorizes third-party apps (FB gets an awful lot of insight from FB connect!) or maybe they just want to solidify their user lock-in.
Either way, I can't imagine they justified the engineering work for massive redesign on seemingly not-profitable properties like Weather/Flickr without having a solid long-term plan for how to capitalize on that.
[1] http://www.engadget.com/2013/08/15/yahoo-weather-android-red... [2] http://blog.flickr.net/en/2013/05/20/a-better-brighter-flick... [3] http://techcrunch.com/2014/01/03/yahoo-sports-gets-ios-7-red...
Actually, the recent changes made me quit Flickr. It's now an ugly mixture of new and old (especially if you use the organiser, etc.) and when you are logged in (which is likely when you use Flickr) you get an unremovable, ugly, purple Yahoo bar.
I was a paying user since 2009. Now Smugmug gets my (and my wife's) money.