EFF: Ubuntu 12.04 will bring OS-level privacy options

As I mentioned, encrypting everything doesn't achieve the same aim, since you can always decrypt it later - unless you destroy the key, in which case you lose all data not just the part you wanted to destroy. You may want to forget the last hour of history completely, so that not even you can retrieve it later. (The best answer, as another pointed out, is not to log it in the first place.)