Update: Digital Homicide has released a statement in response to Valve's decision, illustrating some of the unpleasant comments the team has received in the past from certain Steam users (i.e. the ones they've taken the extraordinary decision to sue), while noting that they're now seeking legal representation against Valve too.
Original story: Valve has delisted developer Digital Homicide's games from Steam, including Paranormal Psychosis, Gnarltoof's Revenge, and Krog Wars. Yesterday, it came to light that the developer is suing 100 anonymous Steam users for $18 million, in response to comments those users had made about the company and its games on Steam. This comes on the heels of an ongoing lawsuit against critic Jim Sterling—who the developer is suing for $15 million—in response to a YouTube video of his blasting one of their games.
A few hours after the latest lawsuit was discovered, Twitter user lashman noticed that all of Digital Homicide's games had been removed from Steam. You can see evidence of that below, and if you search for those games, well, their store pages are gone. (If you've already bought them, or you purchase Steam keys from elsewhere, you can still install and play the games, however.)
TechRaptor posted a story about the mass delistings a few hours ago, a story that has since been updated with an official comment from Valve's Doug Lombardi, who states that "Valve has stopped doing business with Digital Homicide for being hostile to Steam customers".
In addition to its released games being delisted, Digital Homicide's Steam Greenlight titles have also been removed. The only trace that remains of the company on Steam is its Community group, which is not a particularly friendly place at the moment.