I tore apart a Corsair PC Case Fan, and after stripping away plastic, I found this bearing inside. It has swirly grooves. What are these swirly grooves for? My guess is it has something to do with gripping the black plastic, which seems to be insert molded around the bearing and the motor iron.
I think this is a variation of the gas dynamic bearing. Such bearings have a long service life due to the fact that they do not have contact between the rotating and static parts. Air passing through special slots raises the rotating part and prevents it from contacting the stationary one.