Are leaders without titles exist in your organisation? If so, what are the common challenges they're facing?

By leaders without titles do you understand informal leaders, the ones that are team members without having a managerial position?

If yes, I would say there is almost no organisation without informal leaders. In fact, managing them in an effective way is one of the key success factors for a manager. Informal leaders influence their peers. And they do it either conscious, either unconscious. They are like "born" leaders: charismatic, having vision, good communicators, etc. Use them to achieve your goals!

I presume by default they are aligned with the company values and mission. Then, the most difficult challenge they could face is that they are not engaged in organisation's decision process so they don't feel valuable for the team they play for. Loosing their energy will create a loss for the organisation, because they can motivate their peers.

If they are not aligned with the company values and mission, they become toxic for the organisation and the manager has the full responsibility to deal with their attitude. Fast and sharp. As manager you don't want to have centrifugal forces in organisation.   

Yes exists, here are few reasons

1-Lack of opportunities provided by top businees leaders.

2-Flat  organization structure, means very small hierachy scale, people have less opportunity to come on leadership position.

3-No criteria for emerging leadership, means no procedure

4-few un-titled leaders are under-estimated by top business managers

Self-Appointed leaders, influential peers exist in most departmental organisation. Most suffer from lack of authoritarian affluence, experience and formal training with compliance company's rules.