The three Activision-published James Bond games available in Steam's storefront and Activision's official online store apparently made like their namesake yesterday and abruptly snuck out, users posting on the forums (opens in new tab) spotted (via NeoGamr (opens in new tab) ). Luckily, the games didn't mimic Bond's other signature style of causing random explosions wherever he departs.
007 Legends, 007: Quantum of Solace, and James Bond 007: Blood Stone all disappeared with no explanation from Activison, which acquired the license from EA in 2006. Legends, developed by the recently shuttered Eurocom, was released just last November. Blood Stone, developed by the defunct Bizarre Creations, released in late 2010, and Treyarch's Quantum of Solace released in 2008.
Activision probably has a valid explanation for the removal, as missing Steam games don't escape notice (opens in new tab) for long. We'll pass along further information if we learn more from Activision, who we've contacted.
(Thanks to commenter subedii for the Activision store tip.)