It's not marketing. The company that makes the screens can't keep up with the demand.
It's not about marketing - the best marketing is not to create "hype" that it can't be found, as that is not happening in any major way - the best way for the Kindle to succeed is to saturate the market as much as possible.
The "hype" thing only works with products with much more mass appeal than the Kindle. For smaller products, limited production actually hurts it as people look to other products (like the Sony Reader) instead of waiting.
But, the wait is shrinking.... I've heard that it's 2-3 weeks now. And getting them on eBay hasn't cost much more.