Megachurch

If you take close look at events on and after the day of Pentecost, you'll notice:

1)  The little gathering in the Upper Room before the Spirit came was about as big as a typical church of any denomination today -- about 100 people, 120 to be more exact.

2)  The church after the day of Pentecost contained 3000 men.  Assuming their households are not included, we have to add those, if they are residents or have their families with them.  This reckons to, say, 15,000 souls.  There was another conversion later (Acts 4:4), where the head count of men in the church increased to 5000, or perhaps another 5000 were added.  If the latter, and if this count does not include households, we're now talking about 40,000 souls.  All this assumes a household count of 5, including the head.  This is probably small.  Even if the church grew to only 5000 men, then assuming 5 per household, this multiples to 25,000 souls.

One concludes from this calculation that the initial task of the apostles and elders was to take up emergency measures to handle church growth.  We know later (Acts 6) that they set up 7 men to act as "deacons."

So, we conclude that 11 apostles and 7 deacons could take care of 25,000 - 40,000 church members, including dealing with the funds which were brought in due to the sale of property (Acts 4:32ff), and the logistics of distribution to widows, etc. (Acts 6)??

No.  We do not conclude this.

There's no way 18 guys could take care of this.  We have to conclude that a barely functioning infrastructure (there were complaints) was set up to help the leadership do this job.  We have to conclude that those 7 deacons were leaders and managers of the relief effort.  We likewise have to conclude that the apostles had help in their particularly pastoral duties.  After all, it's clear that at the time of the Jerusalem Council (Acts 15), that there were a lot of elders and leading brethren under them!

Therefore, the mere statistics of this episode show that elders and deacons are the leaders and managers of a much larger pastoral and ministerial effort to care for church members spiritually and physically.

As a consequence, when we see the blessing of church growth among ourselves, it is mandatory that we, by the wisdom of the Spirit, also imitate the early church by creating the necessary pastoral and diaconal infrastructure using reliable church members in order to carry forward the work of the church.

Any other approach will lead to organizational failure and leadership burnout.

I started out the day opposed to megachurch.  Hmmm.

If a church happened to gain 30 members every two months and stopped losing folks out the back door, they'd need to be ready.

PS:  Information about the total population of Jerusalem at feast time (such as Pentecost) varies from 600,000 (Titus, in AD 70) to 3,000,000 (Josephus).  Another source states, 120,000 - 200,000 (presumably not just at feast time) in the time of Herod the Great.  Edersheim says people camped out during feast time.  Some claim that Jerusalem was 70,000 - 80,000, but this is probably not at feast time, when huge crowds of pilgrims would come to the city.