Encrypting the DB

With the recent news (almost monthly) of sites getting hacked and user data compromised, I was wondering if there is a way to encrypt the DB (or at least some of the tables such as the ones that store user information), so in the event the site is hacked it will be harder to extract the info from the table.

What are your thoughts,
Chaim

Ps. I do realize that there might be a slight hit on DB performance, however I do believe it is worth the tradeoff.