Last year, Matt Cutts reported Google supports the NOODP tag.
It's a simple but convenient little tag the prevents Google from importing your directory listing as the decription used in organic results.
Now comes word that Yahoo! has introduced the NOYDIR tag. Functioning much like the NOODP tag, it excludes titles and abstracts from the Yahoo! Directory.
The goal is to allow webmasters the flexibility to have the content titled and described as they want it, not as an editor prescribes it.
However, it should be noted that for the most part, the default for a site description, unless the description tag is employed, the default tends to be the first instance of readable text on the page. And in some cases, that can be ugly.
Matt's example is great, understandably so, so check it here.
Have a good one.
~ The (SEP) Guy