My very first DIY project at Brooklyn Row House was wiring the place for CAT5 ethernet. I decided to do this even before I had an inkling of what I intended to do with the place, or even where my office, bedroom and computers would eventually be located. In retrospect, if I'd guessed back then I would have been dead wrong.
Streaming media was still pretty much of a pipe dream in 1999 but I knew it was coming Real Soon and I wanted to be ready for it. I needed a wire soffit between the three floors for cables so I installed fourteen feet of 3" EMT tubing between the basement ceiling and a second floor closet. Through this I pulled six sixty-foot CAT5 cables, four lengths of four-pair phone wire, a pair of coax cables (my satellite TV at the time required one for each LUN) and a bunch of twisted-pair bell wire for a future wired alarm system. It fit but, suffice to say, I probably should have gone with 4" EMT.
The coax, phone and alarm wires were eventually enabled but a funny thing happened with the CAT5. I never used it. Their tails remain coiled, labeled and attached to nothing. What happened? Wireless got better. While wifi was definitely slower than wired ethernet, it served my needs so I tacitly abandoned my plans for ethernet ports in every room (along with beer taps and air compressor ports on every floor... seriously, I half considered those as well).