As long as you're not using gigabit ethernet yes, Gigabit ethernet uses all 8 wires. Standard ethernet (both 10 and 100) leaves 2 pairs unused. I think there may be a caveat if you're using power over ethernet as well, but for standard network runs, 4 wires are never used. This CAN result in noise in the video signal (especially with long runs) and MAY cause minor interferences with the ethernet data, however the high common mode rejection of the typical twisted pair cable shouldn't cause you to worry too much. Your mileage may vary.