Real Names, the SEO takeover, and the YouTube Anschluss were really only the icing on the cake.
The first drove me to kill my personally ascribed account and create one under this nym which I use in a few places online. The second largely dismayed me. Things looked up briefly a year or so back as search got more powerful and enough interesting content had accumulated to provide some actual utility to the site. Last May's redesign, the War on Words, and the YouTube Anschluss were all pretty awful.
That ended with mass-market availability, but it's provided steam to roll on for a while.
Google had an initial base which was, I think, the seed around which it could have grown a community but blew it by releasing publicly too early.
Among other failings.
Their go to market strategy was essentially the same as the Chinese government-run construction companies that build an entire city from farmland, cut the ribbon and expect a stampede.
Getting it right is complicated and I couldn't do it justice in an HN comment, but generally I think they should've focused on a specific winnable market and grown from there.