"Obey your leaders"

17 Obey your leaders and submit to them, for they are keeping watch over your souls, as those who will have to give an account. Let them do this with joy and not with groaning, for that would be of no advantage to you (Heb 13:17).

V17 is often quoted without regard to the literary and historical context. But what was the basis for their authority, and how does that relate to our modern situation? Let's go back to v7: 

7 Remember your leaders, those who spoke to you the word of God. Consider the outcome of their way of life, and imitate their faith. (Heb 13:7).

That apparently refers to Christian leaders who founded the congregation. They've since died. And 13:7 points back to Heb 2:2-3:

3 how shall we escape if we neglect such a great salvation? It was declared at first by the Lord, and it was attested to us by those who heard, 4 while God also bore witness by signs and wonders and various miracles and by gifts of the Holy Spirit distributed according to his will (Heb 2:2-3).

The leaders in 13:7 seem to be the same group referred to in 2:2-3. So what qualified them to be leaders? That passage grounds their message in a chain-of-custody. They were eyewitnesses to the ministry of Christ. That includes the Eleven disciples. However, thousands of people in Palestine–both Jews and Gentiles–had firsthand knowledge of Christ's public ministry. So initially there was a large pool of informants. But by the time Hebrews was written (c. 60s?), that generation is beginning to die off.

The leaders in v17 succeeded the leaders in v7. But presumably they were taught by the eyewitness generation. Similar to Lk 1:1-4. 

This was before the NT canon had been collected and widely disseminated. Many Christians were illiterate. Few Christian owned private copies of the Bible. 

In a sense, Christians with firsthand knowledge of Jesus were like living, walking New Testaments. You had an oral Gospel. In some measure, the Gospel was transmitted by word-of-mouth.

But of course, the generation with direct knowledge of the historical Jesus was dwindling. That would be replaced by the NT. 

Nowadays, clergy and laity have the same source of information. So they don't have the same kind of authority.