Being a leader is a position of service, not a position where other people serve you.  The more that I was recognized as a leader, the less control I had over my own time and energy, and if you have one person at the top (as in the guilds in the games I played) he has almost no control over his own time, if he's going to be a good leader.  The vast majority of his time will be spent building up and helping others.

It is easy for a leader to lose touch with the average members.  Often it seems that the 'leadership' forms a clique.  That group is strong and solid, but due to some exclusive tendencies and habits, they don't stay in touch with everyone else well... and people will leave or drift away for that reason.

It is likewise easy for a leader to start to think he has some real power, and to like it.  Aspiring to lead is one thing, desiring to dominate is something entirely different... and bad.  People will often try to hang on to this 'position' long past the point they should have given it up.  This is always detrimental, sometimes extremely so.  Sometimes the members will try to keep a leader in a position he should no longer have, I have seen this, and it is also very detrimental.

Often a leader will enact policies that he was strongly opposed to on principle prior to taking the leadership position.  Once this happens once or twice, it can quickly spiral into what become some very bizarre changes, even if incrementally.

Sometimes a leader will fall into the trap of thinking he's actually superior in some way to everyone else.  "They made me a leader because I'm better at..."  This is dangerous.  And generally not true.  It leads to an 'us vs them' mentality, viewing the 'people' as 'mindless sheep' who can be 'guided' where they don't want to go.  A leader typically ends up in an official leadership position because he was doing the work of a leader.  It has nothing to do with talent or superiority, but rather with effort.