Now that incandescent bulbs are almost gone, I wonder if it will become common to have wires carrying DC in the ceiling instead of every bulb having to implement the AC to DC conversion as cheaply as possible.

With renewable energy and local batteries, it would make sense to have DC wiring. It used to only be that off-grid systems had batteries (usually lead-acid), and they always just use an inverter. But now with battery packs such as the Tesla Powerwall, even grid-connected houses have DC storage.

Unfortunately, Powerwalls and other similar products are made with built-in inverters and connect only to AC, there is no DC tap. And there aren't any standards around DC wiring and small appliances, so it isn't likely to get traction.

I'm mentioned before (https://news.ycombinator.com/item?id=21109247) that I've seen a DC installation at a friend's house, he used 12V cable lights and DC bulbs, so it seems to work.

I have DC powered under-cabinet lights which are definitely flickering at some fairly high rate.

Imperceptible if you are just looking at it, but in a dark room if you move something quickly in front of it you can see the strobe effect.

But where is the DC coming from? If it is a cheap power source (a rectifier plugged or wired into AC), the DC into the lights could be intermittent, and so cause flicker. For true continuous DC, you need a good rectifier or get the current directly from batteries.

Then we can also use this for our video camera’s and wireless access points. Maybe we can add network to those cables. Let’s call it “power over ethernet” ;)

Ubiquiti has got you covered:

https://unifi-led.ui.com/

The real cheap filament style bulbs are a rectifier, and nothing but.