Originally Posted by earthwormjim
They might be an improved sleeve bearing design, but I don't see how they can escape the issues that fundamentally plague sleeve bearing fans. Reduced performance over their life-time, increased noise generation as they wear and reduced life depending on how they are mounted.
They aren't all bad. It just depends how you intend to use them. If you are running low speed fans(especially sub 1000rpm 120mm), then a sleeve bearing will make less noise than a 2 ball bearing fan*. Ball bearing fans also increase in noise as they age, and since they last longer, they will be louder before they die. So you may be better of getting sleeve bearing fans and replacing them.
Give this a read: http://www.nmbtc.com/fans/white-papers/fans_ball_vs_sleeve.html
*some exceptions, read the paper
Summary of the paper: (Click to show)