The feature is so they can show news that is 100% dedicated to what you search for without knowing who you are and what you have searched for how are they meant to do this? (it is like you expecting me to know everything about you even if you do not tell me your name, if I don;t know your name it is extremely difficult to find any info on you, however not impossible)
The only other method I can think of off hand is to store search info in cookies BUT the problem there is that as soon as you clear your cookies of the cookie expires the age would be back to square 1 which would make the feature useless, another alternative is to link the IP to searches but the problem there is you are assuming the users IP will never change which is obviously not the case (in fact AOL customers can have different IP's between page loads).
Therefore the only way to do it properly is to have the person create an account and store that information with their login. Remember however if you are not logged in when searching they will not count for the personalization as google do not realize you are that user.