As an example, imagine the word "bat" - depending on whether the searcher is a keen bat watcher or an avid sports fan, this could mean two very different things. The difference between American and British searchers looking for baseball bats or cricket bats, for instance, could cause some confusion. Personalised search works by tracking which results are clicked on, and offering the correct category of results with a heavier weighting for individual users. After a while, the avid bat scientist will stop being offered sports bats and only see results about his cheeky little furry friends.
As such, it has recently been announced that this service has been taken one step further by Google, who are now offering the same level of personalisation on Google Video. The system works slightly differently this time, in that the personalisation is offered once the user has added a set of "recommended videos" to their own account, as opposed to the Google algorithm doing this automatically. Google offers the example of the word "grid" - comparing the previous high incidence of music videos and assorted random content to a strict offering of videos and information about grid-based computing once the user had entered his preferences and preferred results.
Many users and industry pundits are worried about the expansion of personalised search, due to the fact that people don't just have a couple of interests or pastimes in their life. It's entirely possible that there are people out there who like nocturnal bats and enjoy the odd game of baseball or cricket as well, and wish to see videos on both of these.
Successfully identifying the correct results on which to base results is a tricky task for any search engine, but with Google on the case we can expect to see a comprehensive middle ground between user-tailored results and a decent array of related results that may be of interest to the user in question.
