I just saw a video where a Wizard farmed yellows in Act I killing as many Elites as fast as possible. He only picked up the rare items, no blues, no gems etc. Just gold and yellows / uniques.
I usually do something similar, but I pick up blues and other goodies, like gems, as well. Usually the blues are not that good, but I still check and vendor them.
Here is my question: Is it worth picking up blues on such runs or is counter productive as the time invested could be used to farm even more yellows?
This is all assuming you can survive in higher Acts and you just crush everything in Act I.