Not only is the TV show supported by the commercials (and anyway, if you're smart enough to use a spam filter, you're probably smart enough to use commercial advance on a DVR), but the other thing wrong with the analogy to me is that the ratio of reasonably palatable to nonsense TV commercials is much more reasonable than on e-mail. Think about your spam box... most of the junk mail I actually read in there is stuff I subscribed to and could unsubscribe from (e.g. ads from Guess, Bluefly, etc, etc). I put it in my junk box for convenience, but it isn't really the "spam problem."
The actual spam is far more absurd than TV ads, except perhaps in the wee hours. Even the most ridiculous TV ads are not as bad as those creepy ads with misspelled cialis that don't even link to a website or phone number, and are just filled with random junk about enlarging your penis.
I think it's rather like I only really watch primetime TV, and yet I'm getting tons of the equivalent of 3AM commercials for phone sex in my spam box.