As of January 2009, Archive Team no longer considers Yahoo a dependable location for data.
This is not based on their engineering, which has shown itself to be consistent and with few outages. Rather, it appears the company is in relative free-fall with regards to which projects they will maintain and what comes under any given knife for cost-cutting measures.
When a company enters this sort of spiral with regard to one of their core businesses (hosting and providing of information services), and consistently gives little or no indication of their next move, it becomes incumbent upon the users of that service to either demand changes in policy, or find alternatives, even poor ones, and build those up.
When a company decides (or, more accurately, someone with the company decides) that a website or sub-site is no longer viable, then it's living on borrowed time. Like a store closing, or a very sick pet, it becomes a matter of how to bring things to a close. This is entirely up to the closing party, and from their behavior, we can see how they will consider doing this.
Previously, Yahoo showed some level of restraint in how they would shut down services. For example, when Yahoo! Photos, a photo sharing site, was closed in favor of the bright and shiny new property Flickr, it was announced, a special site was provided to assist users in transferring their photos to other sites, and there was an opportunity to purchase an archive CD of your content. . It should be noted, however, that Yahoo! Photos was closed under much protest and duress of the userbase, who in some cases had no interest in transferring to Flickr and wished merely to maintain their own interface.
But now, Yahoo seems to have no issues with very quick shutdown, with little warning, and almost no regard for the quality of the site.
Some examples of this new behavior:
- Yahoo is closing GeoCities down "later this year."  Time to start mirroring...
- Yahoo closed Brickhouse, their in-house development and prototype department (think of it as an incubator) in December of 2008. They were swift enough to close down the building within weeks. 
- In December of 2008, Yahoo began layoffs at Flickr, a site previously untouchable, including George Oates, who designed the interface of Flickr, and championed the site's interaction with the "Commons", including the US Library of Congress, and making Creative Commons licenses the default for Flickr's photo uploads. Oates was laid off mid-trip on a fact-finding and information trip for Yahoo, having met and advocated Flickr to a number of prominent folks. 
- On or about January 27, 2009, with absolutely no notice, Yahoo Pets was shut down, all content removed from the web, and completely redirected under another Yahoo property, Shine. 
- At the end of 2014, Yahoo! gave three months notice that it will kill Yahoo! Directory. Now what is left?
Please do not use Yahoo or Yahoo-owned sites for any non-retrievable personal data.
Non-retrievable data means that there is no export function, or way to pull your personal data off the site. You should continue to use it if you can be assured that the Yahoo function you are using will not dramatically affect your life if it disappears tomorrow. Because it might.
In 2014, we invested in our strengths - search, communications, and digital content. To do this, we’ve sunset more than 60 products and services over the past two years, allowing us to focus on the offerings that matter most to our users.—Amotz Maimon, Chief Architect
The following list may be incomplete and outdated. For a more comprehensive and up-to-date list, see the Woohoo page.
- Maktoob Forums
- Yahoo! Answers
- Yahoo! Blog
- Yahoo! Briefcase
- Yahoo! Buzz
- Yahoo! Directory
- Yahoo! Education
- Yahoo! Groups
- Yahoo! Messages
- Yahoo! Upcoming
- Yahoo! Video
- Yahoo! Voices
And a Short Time Later....
- Blake Irving, Yahoo! Chief Product Officer, showing his proficiency for trashing things
Follow their last deeds at https://twitter.com/YahooVictims
- Peter Bright. "Yahoo killing off Yahoo after 20 years of hierarchical organization". Ars Technica, 2014-09-26. Accessed 2014-09-28.
- "List of mergers and acquisitions by Yahoo!" at Wikipedia
- "Timeline of Yahoo!" at Wikipedia
- What Happened When Marissa Mayer Tried to Be Steve Jobs