[porpoise]

“We cannot judge either of the feelings or of the characters of men with perfect accuracy from their actions or their appearance in public; it is from their careless conversations, their half finished sentences, that we may hope with the greatest probability of success to discover their real characters.” - Maria Edgeworth

It's interesting to think about what is it about keystrokes that tend to make people worry about privacy. I don't think it's as simple as "they are storing a lot more data than I assumed". It can't just be a matter of degree. The reason must be broadly along the lines given in the Edgeworth quote.