I'm not a fan of the one ceramic ball theory.
Rest assured the theory is a valid one. I do agree with you that one should not put it into practice which is why I just threw it in as an example.
I do not even know if such odd bearing exists.
@Tokyo Drifter: There's a lot of rubbish bearings out there but what I state is actual fact, scientifically proven fact.
Naturally field experience may differ but if a bearing replacement is correctly executed I see no reason why it should be any different from a factory installed one. Especially so with cup and cone bearings.
On a more personal note, I've run Campa USB bearings since their inception on just a few drops of oil, no seals whatosever and that's it. They've seen the better part of 100.000 km and they're still like new.
Same but less mileage so far for the CULT version + ceramic hybrid BB (a ISO square Ti axle running on CULT ceramics cups and cones!), pulley wheels etc. Not a single bearing has been replaced since.
I am very certain that if full steel bearings would have done the same mileage under the same conditions they'd all have been replaced at least once by now. Not so the hybrids.
Yes, they're top quality but then rubbish in rubbish out and that goes for full steel bearings just the same.
Ceramics hybrids need a little more care when installing, especially so the industrial cartridge types, as the balls can easily dent the races when hammered in (as I so often see done by even the most experience mechanic) but once installed they should run like forever in a bicycle.