Google has changed the way they do things again! And you, as the website owner need to be aware what's going on.
Google is always looking to find new ways to help the searcher find things quicker, and its this new change that is a combination of 2 services.
One of these has been around a while, the next one has just appeared.
Let's  look at the new services: Google Suggest - This happens every time you do a search online, you will see the drop down box which "suggests" what they think you are looking for.
This is has been around for quite a while and almost all search tools online, including Yahoo and Bing are also doing the same thing.
What has changed recently is the way results happen which is the new: Google instant -  This tool feeds from Google Suggest and it does 2 things, firstly it provides grayed out results suggest results in the actual search box.
In the second part is that now the search results now actually change on the search page.
What does this mean to webmasters? It means that more and more search will go to the long tail search, the longer search terms (2-3 words) will increase as searchers "let" Google tell them what to think.
This makes it easier for the user to find what they are looking for without having to type the actual words AND actually show them words they may not of thought of eg: X product...
discount (the searched may not have thought of discount) Think about that...
Users don't need to type more.
This is aiming to those essentially lazy and wants results now.
This may mean a spread of the search volume, it means that larger terms won't get as many visitors and smaller terms will get visitors they didn't get in the past.
Also this will mean that the Google AdWords external tool, which most Webmasters use for Keyword research, which based on previous history, will be out of date.
I believe this is more of a win for the owners' of sites aiming at the 2, 3 and longer keyword terms.