[michaelt]

Yeah, it's fine for USB cables. The difficult bit would be if you're planning on cabling an entire office building from one low voltage DC source, like the solar panels the article mentions.

If you want 60 watts at 20 v is 3A, and if you want to supply a hundred ports with that you're going to need copper cables the size of your finger.

[tanzam75]

A standard is currently being developed for DC distribution in datacenters and commercial buildings, at 380 volts.

One of the proposals for residential DC is to supply 380 volts and 24 volts. The higher voltage would be for things like space heaters and hairdryers, while the lower voltage would be for electronics.