DLW - 12/19/93 - the reason ball and roller bearings were so popular in
                 early high performance engines was probably due to their
                 ability to tolerate old-timey lubricating oils, which were
                 pretty crummy by modern standards.  That's also probably
                 why lots of manufacturers hung onto roller lifters long
                 after they'd gone to plain bearing mains - cams were high
                 wear items.

 Motorcycles probably hung onto rollers so long because they ran very hot, and 
older (pre'80) oils broke down rapidly with temperature.  Rollers need very 
little lubrication, mostly between the rolling element and the cage.

 Modern racing engines use plain bearings because they can handle much higher 
loads than roller bearings of the same size, particularly shock loads.  You 
can also change plain bearings without having to disassemble a multi-piece 
crankshaft.