Can people really be all they need to be?

As Dr. Jih was talking in class today, he mentioned how a company he knows of can't hire people because they simply can't find the "right" person. With the way technology is growing is it acceptable to ask that someone be as up to date with technology as it is with itself? Can one person simply know all there is to know? I'm not to sure of this answer to be honest especially when it deals with technology. It changes so much everyday so how are we to know when someone knows everything or we think we ourselves know everything. Sometimes companies will just have to hire people who fit the bill and who are will to learn as technology and the industry evolves and quit looking for that "ideal know all candidate." Companies must make their expectation realisitic and if someone is will to learn with the changes then so be it.