Gabe Newell has told Engadget that, despite the speculation (including our own) that a hardware project may have been cancelled, that Valve haven't cancelled any ongoing projects at all, and that's the the reason behind their having let some staff go. He added, "We're not going to discuss why anyone in particular is or isn't working here."
RPS is pretty certain that Valve has let around 10% of its employees go in the last day or so, around 25 to 30 staff, but Valve has refused to discuss this. Reports from Gamasutra seem to suggest that even the hugely respected director of business development, and a very key figure behind Steam, Jason Holtman is one of their number. RPS is trying to confirm this.
Newell's brief statement to Engadget reads,
"We don't usually talk about personnel matters for a number of reasons. There seems to be an unusual amount of speculation about some recent changes here, so I thought I'd take the unusual step of addressing them. No, we aren't canceling any projects. No, we aren't changing any priorities or projects we've been discussing. No, this isn't about Steam or Linux or hardware or [insert game name here]. We're not going to discuss why anyone in particular is or isn't working here."
Meanwhile, Garry's Mod creator Garry Newman ran a one-month Diff Checker search on Valve's team page, which revealed a number of known names no longer appearing. Along with Holtman, these include artist Moby Francke, TF2 character animator Keith Huggins, L4D and HL2 software engineer Tom Leonard, Portal dev and former Narbacular Drop Digipen team member Realm Lovejoy, test lead Marc Nagel, animator Bay Raitt, engine programmer Elan Ruskin, and TF2 "Meet The" video series animator Matthew Russell.
It's worth noting that Valve hasn't responded to emailed enquiries from RPS (although that's certainly nothing new for us), nor to many other gaming sites who approached them for comment, instead picking a respected gadget website to give their sole quote. There certainly haven't been any public statements expressing regret at losing any staff, nor thanking anyone for their work for the company until this point.