Well, since you both asked...

I joined Yahoo in the Mobile division soon after the Flickr and Delicious acquisitions, when it looked like Yahoo had grasped the importance of including social elements and user-generated content into its experiences.

Fundamentally Yahoo is an advertising company that failed to understand the value of self-serve, long-tail advertising. It preferred the high-margin, high-touch sales approach with big media customers that had kept them alive through the first dot-com crash. Fair play to them: clinging hard to those media dollars was absolutely the right move for survival. But they missed the boat and, critically, failed to acquire Google for $1bn -- something that Semel seriously discussed with Page and Brin sometime around 2002.

The next-best thing after failing to buy Google is create their own. They did this by buying Overture and Inktomi, which together became the core of the post-Google Yahoo Search (remember, search on Yahoo was powered by Google until 2004). In terms of search accuracy, Yahoo had roughly matched Google by around 2006, but on the monetization side their algorithmic yield-optimization for keyword ads was awful compared to Google, and despite massive engineering investment remained so until they got out of the game by selling to Microsoft in 2009/10 (not that Microsoft is much better at that, I hear).

If you accepted that they had missed the boat on self-serve keyword advertising (which internally nobody ever did), the next-best thing they could do was massively increase page impressions by creating a blockbuster, high-page-view, sticky product. This would maximize the value of their still-excellent display ad business. By 2003/4, it was clear that social networks, like Friendster and relative newcomer MySpace, were exactly that kind of product. Here again, an acquisition would have been smart (though less obviously smart than Google).

Instead Yahoo tried to get into the game with Yahoo 360, a home-grown social network. This was at least the right strategy, but here again they simply failed on execution. 360 was buggy, ugly, confusing and lacked activity streams, which turned out to be a key feature of Facebook's subsequent success. No bones about it here: they had a gigantic number of users they could drive to 360 from the front page. If 360 had been at all compelling, they could have dominated social networking overnight.

So, four major failures behind them, in 2008 they saw the huge success of Facebook and tried to turn social: thus came YOS, the Yahoo Open Strategy. This included new Yahoo Profiles (a second attempt at social networking), and YAP, the Yahoo Application Platform, the last product I worked on before leaving. YAP was supposed to be a sort of cross between Google App Engine and Facebook Apps, where we would simultaneously distribute your app via our social streams and scale it on our infrastructure. This was a brilliant idea, I still think.

But the execution was a clusterfuck from start to finish, the gory details of which I'll skip. The final product was nothing like the original idea, and ended up a half-assed knockoff of Facebook Apps, but without any kind of traction. And in the meantime, it turned out Facebook Apps were a flash in the pan and Facebook had pivoted to Facebook Connect.

So that's my four years at Yahoo: missing one big opportunity after the other, despite multiple swings of the bat. It's not that we couldn't see what needed to be done. We just couldn't, organizationally, move fast enough and bravely enough to get anything good out the door before somebody else ate our lunch. And I didn't see that changing any time soon, so I left.

Which is a shame, because I really love Yahoo. It's a good-hearted, fun company, good to its employees, and full of people who genuinely care about our users and building great things that improve people's lives and make money at the same time. But sclerotic management and organization seems to have doomed it permanently to mediocrity. It's not going to die, but it will continue to lose relevance.

[To my fellow Yahoos who read HN: I hope you don't think this is too harsh. I love you guys!]