How Classification of Page Elements and Search Results May Influence Alternative Titles and Snippets Displayed in Google, Bill Slawski, SEO by the Sea (Jan 26)
For many years Google's snippets were mainly keyword-in-context. Today, Google does more massaging of title and snippet as it tries to make sense of the page and present a better result to the user. A recent patent suggests that Google may be going so far as to "classify" it in order to make decisions on title and snippet.
"The patent provides a very detailed look at how Google might go from classifying queries (using a lookup table, or via some other method) to classifying the different elements of a search result such as a title, snippet, and URL in that result. Those classifications might be weighted somewhat by the position that those pages appear at within search results as well."
From Google's posting - "Google’s generation of page titles and descriptions (or “snippets”) is completely automated and takes into account both the content of a page as well as references to it that appear on the web. The goal of the snippet and title is to best represent and describe each result and explain how it relates to the user’s query."