What does the number 150 have to do with missions?

Seth Godin recently wrote a post about Dunbar's number being the law. The "theory" is that a human can only handle 150 meaningful relationships. Obviously, you can have a lot more acquaintances than that as many of us have several hundred friends on facebook. But the truth is that we can't physically, psychologically, or emotionally handle more than 150 significant friendships. Now, this causes a problem for the missionary because it is such a relational line of work and we need real friends to accomplish our task and not just twitter followers.

Think about how many personal friendships someone on the mission field needs to keep up with:
1) Supporters: The book Friend Raising basically teaches us that raising support is a relational activity. We're not just asking for money, we're looking for partners that can be a significant part of the work and that means intentional relationships with people back home including our family, home church, financial supporters, prayer partners, etc.
2) Co-workers: Most missionaries have a network of people in their organization (both home and field staff) and peers from other agencies that they stay in touch with. In order to have a strong team, it's essential to spend a significant amount of time building trust, praying, talking strategy, etc.
3) The Church: Christians must be plugged into some local body of believers. The church is to be a community of people living life together while focused on Christ rather than a one day per week event which takes time and being intentional. Many church planters also spend significant time discipling and raising up the national leaders. Truly investing in people's lives takes time and a church truly living out community takes effort.
4) The lost: Most Christians end up having only Christian friends because their 150 quota gets filled very quickly with church activities (small groups, awanas, softball team, choir, etc.) leaving little room for significant relationships with non-believers. Missionaries should have a room in their network for several folks that don't know Christ.

These are just some very broad strokes and I'm sure that there are many other categories as well. How can missionaries manage their time and relationships better to see all peoples on earth reached with the Gospel of Christ? Is it even possible for a missionary to juggle the many relationships that are required for successful ministry? Any ideas on simplifying