Pretty much any fan unless it is a "ball bearing" fan is either a sleeve or sleeve like bearing with fluid to assist in that bearing design. Nano can mean fancy coating or fancy plastic, or...?
With that said, I don't find the bearings normally being responsible for the majority of the noise, it's normally the electric motor and fan blade that's responsible for the noise. I do think ball bearing fans can be made with less friction though and the less friction, the less motor power needed and likely less motor noise.
Anyhow, the NB fans are one of the better in noise quality (Smoothness) despite the gimicky "Nano" naming convention.
You could take tap water from Minnesota and call it "Super-Silver-Nano-Sota-Soda-Ultra" and sell it for $10/liter if you put it in a fancy bottle with a purdy label....Edited by Martinm210 - 10/14/11 at 10:08pm