Matt Cutts was the head of web spam for Google for several years, and wrote an influential blog on the subject of Google search. The blog still exists, as does Google, but Matt Cutts moved on to work for the US Government, as the head of Engineering for the United States Digital Service (USDS).
With Google, Matt Cutts moved from search quality into web spam, and as such, is the authoritative voice behind a lot of “white hat” solid, fair, SEO techniques which actually work.
He subsequently moved into being head of web spam, which means he spent a lot of time working on removing over optimized (also see spammy) things from Google’s index, algorhythmically.
Cutts is perhaps best known for his blog, Matt Cutts, Gadgets, Google and SEO, which is where most of the early days SEO world would congregate to learn about what Google was actually doing. He also regularly featured in official Google videos relating to SEO, as well, many of which, while no longer specifically relevant, make great background viewing for anyone looking to learn the history of search -and search engine optimization.