If the site is relevant I have no problem with people buying links to manipulating the serps. If you are not high in the serps, you wont get traffic and you wont receive backlinks, so starting off, do what you can within reason.
I just did a look to see how well represented my site is in Yahoos directory, and I discovered I have 24 pages listed in 24 different Yahoo directories. All were "volunteer" listings. Only a few pages were really key pages for my site, but that's still pretty cool. I was thinking of trying to submit my site to some specific directories, but maybe I'll wait.
I think what I need to do is talk with someone who is really good at picking the best directory to suggest Yahoo to list a site in.