The days of wired keyboard and mice are mostly over, even for desktops where having an extra couple of wires isn't a big deal. Unless one's system is equipped with Bluetooth and paired with all Bluetooth devices, wireless keyboards and/or mice will take up USB ports.
While some keyboard and mouse combos (sold as "wireless desktops") can sometimes share a receiver, it's usually of the bulky variety. Logitech now improves upon things by taking its 'nano' USB receiver and making it compatible with a several choices of keyboards (the both ergonomic and traditional choices of K350 and K340) and mice (M705 and M505 for desktops and laptops).
Of course, the draw of the nano receiver are strongest for the laptop market, which rarely needs an external keyboard. And those with desktops haven't been crying out for more compact and portable USB receivers. Nevertheless, the technology for both desktops and laptops are merging, and we're not going to complain about that.
Check out Gizmodo's gallery for more pictures of the new products.