I have been looking at Google Labs and their NGram viewer, which allows you to research the use of any word or phrase in the book corpora of (so far) English, French, Hebrew, Russian and Spanish from 1800 to 2000 and spot trends.
I have been playing with this and offer one example. 'You' fell from a peak of over 2 instances per 1000 printed words in 1900 to just over 1.2 per 1000 in 1965 (a 40% drop!) before rising again over the past 40 years.
Why did 'you' fall so dramatically out of favour? Why has it revived? Was 1965 a particularly selfish year? Are we now writing about others more than about ourselves?
Perhaps not. Certainly the long-term trend for 'I' is quite similar to 'you' with a peak at about 1900 and a steady decline thereafter (although since 1980 and the rise of the New Right it seems to be on the increase again). Even so, at 3.5 per 1000 it is still twice as common as 'you' and more common than any other pronoun. Our favourite subject is still ourselves.