I'm tinkering on a new cartoon project in my spare time and I'm contemplating doing it in 4:3.

Would it be a tragic mistake to make a long-ish cartoon in 4:3? (The cartoon would be sold on DVDs through the internet.)
What do you think are the downsides of working in 4:3? For example, if by some miracle my cartoon became wildly popular, would the 4:3 ratio have a negative effect on it's chances of being shown on television? Would 4:3 lower sales? Do some people only buy widescreen DVDs?
My muse says, "You are the creator; if 4:3 feels right, use it." But my brain says, "Are you kidding me? 4:3 is dying as an acceptable ratio for cartoons."
Thoughts?