Do tailored search force us into an individual intellectual rut? Is this a threat?
To really understand the world through the eyes of others - it is not sufficient to randomise the input that we receive.
The existence of a rut is not necessarily a problem, although an inability or an unwillingness to break out of it may be.
Perhaps, as Google builds an increased understanding of us, it might be willing to share that understanding more widely, so that we in turn may start to understand others; both as individuals and as social groups. (For those that are willing to invest the time).
I also hope that over time, the distribution of human culture and practice will change, with an increase in variance, but a reduction in extreme outliers; so we can enhance our diversity whilst placing an upper bound on the risk of misunderstanding and conflict.