All Meta Tags are worthless.

Meta Description is the grand master of uselessness. It is an illusion that most people in general and many experience SEOs fall for.

Have a read of this - from an experienced SEO... Capturing the click through compelling meta descriptions | Searchlight - An SEO blog by Stephan Spencer - CNET Blogs

Quite a logical and impressive deminstration of Meta Descriptions effectiveness [or so you would think]... but doing your own reasearch shows something totally different.

The advice suggested in the article is not just misguided it's not even accurate. The author never even looked to see if there was a Meta Description (he only assumed there wasn't a Meta Description because the available description sucks for the search phrase queries) and as such the author is totally uneducated about "the value and limitations of both snippets and Meta Descriptions"... you just can't trust a Meta Description to be the prefect representative for your domain.

The page in the article has a Meta Description namely <meta name="description" content="Gmail's good but it could be better We've featured several Greasemonkey scripts that enhance Gmail in lots of different ways - like adding saved searches attachment icons label" />

Unfortunately the query for the search snapshot was Lifehacker Firefox extension... and since the Meta Description does not contain the words "Lifehacker" or "Firefox" or "extension"... the snippet still appears by default... which actually shows the reverse claim of what the author claims.

Because a Meta Description can only contain about 150 characters you are extremely limited by it use and if you don't appreciate the complex problems associated with page layout you can do more harm than good absolutely relying on Meta Description to be the appealing reference... If you "fix a page's layout problems your snippets will be equal to any targetted Meta Description and moreover it will cover a complete swath of potential queries rather than only covering your more targeted term.

NOTES: Since the article was written (well posted) on August 20, 2007 11:31 PM PDT and the cache shows a recent date I checked archive.org to make sure the Meta Description was on the page prior to the article post date... it was July 5...

Lifehacker Code: Better Gmail (Firefox extension) - Lifehacker

Ther best advice is avoid using Metas PERIOD! ...they don't help with ranks and they do cause you to feel too secure in how your listings appeals to searchers.