I wish I'd seen this thread earlier. My assignment for today, as better half left for work, was to string up four long and tacky-looking strings of lights, around the garage, a tree in the garden, and down the fence. About 600 leds in total.
Faced with the prospect of up and down ladders, getting stung by rose bushes, and generally wasting a nice sunny day, I would have welcomed an excuse to not do it. And "it'll kill our broadband" would have been an excellent excuse.
But too late, the lights are already up, glowing nicely. I can't see any stats these days with BT supplied fttc modem, but broadband performance seems fine. Of curiousity, I might wander around with a radio tomorrow, see if any undue RFI is being generated.