Basically, Personalised Search means that once you have visited a website, via its results pages, Google is now more likely to offer you the site again, in future search results.

Now, if you're an advocate of personal privacy, an international terrorist, or part of an organised crime syndicate you already know that Google records you're every move and you've worked out a way of turning its tracking off.

However, those of us who don't fit into the above categories have not really been that bothered. But now that Google is using this information to choose websites for us, perhaps we should be bothered.

Fundamentally, I use a search engine to find websites I don't already know about. I have other mechanisms for recalling websites from previous interest; bookmarks and news feeds (RSS) for instance.

And whether my own previous misjudgment in site selection is a good way of determining what sites I see in the future is highly debatable too!

You can of course turn off personalised search, but it is now on by default and few users will be aware of this or work out how to turn it off. Previously you had to be logged into iGoogle to get this 'useful feature' but now everyone is unwittingly lumbered with it.

This makes it very difficult to prove money spent on SEO is justified. If everyone is getting different results, how can you know your SEO is working?

Alternatively, the unsuspecting client, who visits their own website on a regular basis, might think their SEO consultant is doing an amazing job, as their site seems to turn up on every relevant search they do.

So if you're site has suddenly become number one in Google, for your targeted keywords, but this hasn't turned into an avalanche of website visitors - and of course you've read this, you will now know why.

Chris is MD of Social Media and Online PR agency Friend Digital
Email: chris@frienddigital.com Twitter: @ChrisTomlinson1