Why does Google care about meta descriptions?

Official Google Webmaster Central Blog: Improve snippets with a meta description makeover
http://googlewebmastercentral.blogspot.com/2007/09/improve-snippets-with-meta-description.html

We want snippets to accurately represent the web result. We frequently prefer to display meta descriptions of pages (when available) because it gives users a clear idea of the URL’s content. This directs them to good results faster and reduces the click-and-backtrack behavior that frustrates visitors and inflates web traffic metrics.

(via Instapaper)

Help your click thru rate by spending sometime writing a good title and description for any content you publish on your site.

Google says so!