As a few SEOrs will know, Google is in the process of rolling out it's new Google Instant Search. Right now it only appears to be available here (UK) when logged into your Gmail account but the intention is to roll it out worldwide over the coming weeks and UK over the next 7 days.
So what is Google Instant?
Google Instant is real time search results that tries to predict what you want and display the results in the SERPs (search results) as you type and all without having to press enter on a full search query. If you type "W" results for weather will instantly show up, type "Wo" and those results change from Weather to World Cup, type in "Wom" and you will start to see search results based on Women, and all without having pressed the enter key. You will also see predictive suggestions so as you type Google will not only try to predict the search results but try and predict and suggest help with your search query.
What does this mean for Webmasters?
It's hard to tell just yet, but as results are being displayed and predicted before you finish typing, a search engine users eye is drawn downwards to the results, meaning that you as a user may only type in one word of a phrase before finding what you want and they might not be what you would have found if you had finished your phrase as normal.
There could be swings in traffic because of this, maybe not immediately as people get used to the new system, but as they do and it becomes incorporated into their daily search it could well result in less long tail phrases gaining the no1 sport and more shorter phrases doing so.
Example:
If I want to find "Franchises for sale in London" and I begin typing "franchises..." see a load of relevant results promising me franchises across the UK, so why would I go to the bother of completing my phrase "Franchises for sale in London" when I have my desired results already there. However if I was to complete my phrase i would see a different site at position 1. This could mean that webmasters who have targeted long tail phrases are going to see a decrease in search engine traffic and conversions per SERP.
We may not immediately know the full extent of the change in peoples search engine behaviour as they struggle to lose their old ways but over time as the new system becomes widely used we could see some major traffic shifts.
No other update will have had such a huge impact as this one.