The dangers of YES MEN!

Career path of leaders always has a phase where there are tough decisions to be made. One of the decision is between Loyalty and Quality. Not very explicit in several cases as a lot of time personal attachment to followers do happen to leaders. Similar attachment happens with co-leaders.
This attachment is very important in a lot of ways as it helps to build trust and communicate consistently across different strata of organization. However a leader does face the dilemma at sometime-to make a decision to axe a loyal follower as his performance is not shaping up to current requirements or he is the bottleneck in change without he realizing it.
There are some people who ask me "This maybe true long time ago when people had their job from college to retirement and loyalty with companies was a valued asset. Today people move across so many jobs within career. So this dilemma does not occur as personal attachment rarely develops. Most of it is professional attachment". For sure this is true. However when a Leader after reaching a particular level starts to move around will also try to take his loyal followers from other companies with him with a promise of better career, taking care etc. This creates more responsibility on the leaders and this is a form of attachment which still thrives.
To be clearer it is not bad to have some people who are adapted to your style and with right competence with you. But the danger is if after a few years they are able to predict you exactly and become YES MEN. When two people think alike then one of them is redundant is an aggressive posture in driving innovation. Thinking alike is just one part of the problem. The bigger problem is when others start to perceive the special treatment to the follower whom they implicitly start to think is the successor...then there is a negative halo effect happens. There are usually three aspects of any job-routine, tactical and strategic. Depending on the quality of YES MEN they completely say (even if they don't complete believe) whatever leader thinks is right in strategic and tactical aspects. In fact they praise his vision more often than others. The smiling face of the leader (as everybody likes praise) encourages them to enforce their own controls in routine/administrative aspects which will make them indispensable. This where the leader usually is blind as he thinks overall alignment has happened and is going the right way. YES MEN are more dangerous when they start using the leaders name more often to show to the organization(some pick up the phones in a meeting and talk to the leader implicitly trying to clarify something but explicitly to send a message of closeness to the middle level managers) that there is some extra powers he has.
The dangers of YES MEN don't become apparent till there are more than 3. But even one thorn when not trimmed can hurt the leader's credibility. It surely helps to have political strength by having YES MEN but if it starts crossing the professional boundary then it is time for action.