Thomas replaced Nick Denton as the managing editor of Valleywag on July 6, 2007. Valleywag, a two-man operation, was written mostly by Thomas, with help from its former editor, Nick Douglas.
CBS News interviewed Thomas in San Francisco on his editorial philosophy in April 2008. During the interview, he explained Valleywag's purpose, saying, "People get into a bubble [...] Valleywag exists to burst that bubble. Silicon Valley is built on delusions." Thomas also mentioned that Valleywag crossed the five million pageview mark in March, the website's all-time high. When explaining Valleywag's purpose, Thomas stated, "Gawker covers a zero-sum world [...] If you're rich, you'll always be rich. That kind of thinking doesn't translate into our world. [...] In Silicon Valley, anyone can start a company and put out business cards that say you're a CEO." Thomas also commented on life as a journalist in New York City, expressing that "in New York, it's all about sucking up to your editor so you can get the cover and sucking up to other writers. The page-views system says you're answerable to your readers. You people in New York are obviously too busy not changing the world." Thomas was also asked if Valleywag published items to exact revenge on enemies, to which he responded that that was "the most boring reason to write a story. No one cares what I think." As a mainstream technology writer, Thomas often criticizes other journalists who fawn over their subjects simply because they are famous or popular. For example, he once blasted a Fortune writer by saying, "Has he ever written anything negative about a tech mogul?"