Nice reality check, t36kr84.
They were around when I was a kid, and even today skywriters are tolerable and even a little intriguing because they only appear when weather conditions are perfect.
How long before we start seeing visual pollution like advertising on clouds? Once the technology is developed (and this shows it can't be that far off), are cloudy nights destined to be full of junk food and car advertisements? Are there any laws preventing us from being unwillingly bombarded in this way?