Apparently, one thing that is missing here is that it is more of a world of clicks than when the network started and was mostly offline pushing business cards, brochures, TV commercials, where the URL was displayed.
Now, with ads (banner and text), people who post recommendations on social networks, on any email list, everything is clicked, so the old thinking method that has been going around is essentially useless.
Some sites should still be short, sweet and memorable, but they are not so many anymore.
As Billzo points out, once it's marked as a favorite, it's very easy to come back with only the first letters, so a 256-letter domain would work. The story works that way too.
Also, content and domain do not have to match, since people do not pay attention to things like that very often. It's more marketers paying attention. If people paid so much attention, do you think they would click on the links of some of the CPA networks that have something like zxujfs.com as a domain for things like acai berry products?
If you are selling to the sellers, the domain and the products must match, but otherwise, I think you are giving people a little more credit than they deserve to be concerned about such things.