Intel today revealed details on Ready Mode Technology, which is "a capability that takes advantage of new power saving states in Intel's 4th Gen Core desktop processor combined with software and board-level optimizations which enable OEM desktop computers that are instantly ready and always connected while sipping power."
Intel found that the majority of desktop users turn off or hibernate their machines when not in use. This sort of behavior is green, which is great, and absolutely makes sense for laptops since often they're battery powered, but Intel imagines that desktops could be even more useful with its always-on power supply and Internet connection.
To facilitate this, Intel has enabled a lower power C7 state on Haswell as well as the chipset. Intel issued new motherboard design guides for lower power consumption. With the hardware tweaks and special software (supplied either from Intel or motherboard OEMs), Intel claims that PCs with Ready Mode Technology can stay active while under 10 W.
The advantages of having an always-on PC are probably clear to most of you, but Intel gave examples such as having a constantly-connected IP phone, or an always-available media streaming or file serving solution.
Story updated with photos.