This is meaningless. Statistically meaningful tests are performed using ABX testing methods (http://en.wikipedia.org/wiki/ABX_test) with high-quality equipment. And, yes, many people have trained ears (and brains?) that can easily distinguish the artifacts made by the MP3 compression even in 320kbps. See this (http://listening-tests.hydrogenaudio.org/sebastian/mp3-128-1...) as an example of an ABX test.

As for me, with my current medium-quality headphones, I can't distinguish between the original and an 128kbps mp3.