U.S. Naturalization / Citizenship background check -- what is involved?

Hello,

I’ve been a U.S. legal resident for over 25 years and have decided to finally get my citizenship. I know that the FBI (and possibly other agencies?) do a background check before you are approved.

My questions are:

1) What exactly do they look for on this background check, besides your criminal record (or lack thereof)?

2) Does the government also access your social network accounts (Facebook, Myspace, Last.fm, etc)?

3) Does the government Google you?

I don’t have anything to hide, I’m just a privacy advocate and I’m wondering how deep into my personal life the government will dig.

PLEASE DON’T: confuse this with the immigration background check that the government does when you apply for a green card. I have that and am looking to become a naturalized citizen.