Initially noticed and reported by several individual developers, and later confirmed by Valve itself, the Steam platform has added the ability for game developers and publishers to set and manage their own sale pricing, a process that previously involved coordination with Valve. Via Ars Technica:
Reddit user Sharkiller (via Gamasutra) was among the first to notice a post in Steam's private SteamWorks community (developer account required) laying out the terms of the new program. Developers can set any discount price for their game when scheduling week-long sales up to two months in advance or set their own custom discounts for periods of up to two weeks (it's not clear how frequently those sales can be repeated or how long they can run).
Setting the asking price on a Steam game is usually a collaborative process between Valve and the publisher; as Valve notes on the SteamWorks FAQ, "pricing is very title specific, and we've got a lot of data and experience to help you decide on what the best price is for your title. We'll work with you to figure out pricing." This new effort would seem to give SteamWorks developers a lot more direct control over pricing changes—without having to go through Valve for consultation and approval.
Responding to Ars, Valve's Adiden Kroll confirmed the initiative, clarifying the platform holder's intentions:
“As with the addition of a 'Recently Updated' section to Steam, this is another effort to shorten the distance between developers and customers. This new Steamworks tool allows developers to configure discounts for their own products, on their own schedules. They can define custom sale periods or opt in to regularly scheduled sales. This will enable developers to better coordinate their promotions with events, announcements, or major updates they are planning for their products.”
It seems unlikely that this will affect the deep discounting of major event Steam sales, but it will almost certainly affect the frequency that some developers and publishers mark their products down, so hold on to your wallets.