I think it's a perfect storm of advertising, E/I, and cable that killed Saturday Morning - there was no one reason for its death. However, advertising is probably the most significant of these factors. Let's say that ads cost $20,000 on average for a 30 second spot. Due to these limits, you lose 4 minutes of ad time. That's 8 lost advertisements, and most importantly that's up to $160,000 less revenue than non-kids programming.
The loss of particular advertisers also probably hurt. Kellogg's was cited by name as one of the reasons Kids WB dropped weekdays, because they cut advertising once obesity became a top issue. When things consolidate into huge companies, and one company cuts ad spending, it's going to hurt in whatever area they cut the spending.
Okay. That was something that I had conflicting dates on - nobody really listed the actual date that Kids WB would end on, but they did list when Daytime WB started. I just assumed that since Daytime WB began on one day, Kids WB ended the Friday before. There wasn't a hard date like there was with Fox Kids.