I cannot be the first person to notice this, but I made a fortuitous and surprising discovery recently. Having just noticed the three-week-old news that selected shows from FOX were available through ITMS, I was having a look at what they had, and found, with a certain nostalgic excitement, that Lost in Space was among the offerings. What jumped out at me were the running times of the episodes: just under 51.5 minutes. That's about 8 minutes longer than the Battlestar Galactica episodes I'd been downloading. So I dug around some more and here are some rough averages, based on ITMS track information:

Half-hour shows

• The Munsters (1964): 25.5 minutes (85% content)
• Dragnet (1967): 25 minutes (83% content)
• Adam-12 (1968): 24.5 minutes (82% content)
• Saved by the Bell (1989): 22.5 minutes (75% content)

Hour shows

• Lost in Space (1965): 51.5 minutes (86% content)
• The A-Team (1983): 48.5 minutes (81% content)
• Buffy the Vampire Slayer (1997): 45 minutes (75% content)
• Desperate Housewives (2005): 43.5 minutes (72.5% content)
• 24 (2006): 44 minutes (73% content)

While that's nothing like a scientific sample, it still appears to show a clear pattern of replacing content with additional advertising over the past four decades. I suppose it is not very surprising, but still the magnitude of the shift (we now watch almost twice as much advertising per hour of television as we did in the 60s) strikes me as substantial. I wonder if this much dilution of content with filler would be accepted so quietly in any other industry.