That 150 limit also involves your ability to keep track of people's relationships to eachother I think. Which would mean that you should be able to maintain relationships with significantly more people if they're divided into mostly-disjoint groups.
Another area that organizations struggle with is spending the time to put the structure in. They may say, "It takes more effort to put in structure, so while we want to be structured, let's just work harder as we go from 150 to 250, we'll solve it later when we're less busy" Then it goes from 250 to 400, then the next thing you know it's a 1600 person mess. :-)
I don't know if it's even possible, but why not push a small group to become owners of their own shop, outsourcing work to them ? This might push those small groups to seek other connections to the external world and thus build strength and resiliency.
Of course this implies giving up the money. This is probably where the core tension lies. I guess many wouldn't even want to think about it.
Semco (quoted elsewhere) was big on the "fund your best people's ideas" concept to cut loose companies. When you have to get external funding too, it forces discipline. The kerietsu (sp?) concept breaks down during tough times when partial owners subsidize the weaker units in the group. This happened in Japan.
This isn't a simple problem, because there's no one size fits all solution.