Normally it is Googlers defending Google on Hacker News but Ryan Moulton, a software engineer at Google since 2006, who I think works on the Google search team, is defending SEO and the SEO business on Hacker News.
In short, a blogger called out an email he received from a link builder asking to buy or get a link from his site. You and I get them all the time. But this blogger called this the destruction of the web.
In which, Ryan Moulton, aka moultano on Hacker News said:
A large part of SEO is just making it obvious what your page is about. This helps both the user and the search engine. A lot of it is just usability, but usability specifically for a user who is coming from a search engine.
Well, he said that in response to a comment where someone said SEO is a "bad thing."
He explains why sites and business should rank on Google later on:
You should read this as shorthand for "build your business the traditional way and the users will come." Don't just count on ranking highly for a competitive query for your business to succeed. Build a brand and customers, and people will seek you out. You will have no difficulty ranking for [the name of your company] and this is where most good sites get most of their traffic from Google.
Matt Cutts also chimed in there a few times, also on some levels defending SEO as a business practice and also defending Google when needed.
Forum discussion at Hacker News.