Yes men often ruin the productivity or usefulness in the department they work in, as they are unwilling to provide any form of original idea, opinion or more importantly criticism to their boss and thus contribute to disconnect between managers and workers.
Yes man(no spoilers) is also a movie that was produced in 2008 starring Jim Carrey. In this movie he makes a conevant with himself to agree to any opportunity that he may come across.
Some people believe they are living life this way by opening up every possible gate to a better future.
Bob: I saw that a few weeks ago. Im glad I did, I have been saying yes to everything lately and have found the sweetest things in life.
Fredrick: Wow, are you serious!! I am going to become a yes man!
i) they are attempting to get 100% acceptance stats to look 'kool'
ii) they do not like hurting peoples feelings by saying 'no'
iii) they are dumb