There has been a lot of comment on the new personalized search engine rolled out recently by Google, but what does this engine actually do? The features I like are;

You can list the sites you want included in searches. Say you wanted to buy electronics, you could create your own engine that searched only Circuit City, Best Buy and CompUSA.
You can custom display these results on your website, so if you own a network of websites, you could include a search bar that searched only your products. The search would by no means be impartial, but would certainly be good for business.
You can also use a Google Marker to add sites very quickly and easily to your personal engine whenever you please. You can also open up that process to additional users.

The impact on large, well known companies will be positive. People will add sites they know to their search. On the other hand, it won’t be helpful to smaller companies who rely on appearing on the first page of search results to attract new customers. They could be excluded from the new engine. It will be interesting to see how many people actually use personalized search. If it becomes pervasive, then it could open up a whole new pecking order for natural search.