A few thoughts here, in no particular order:
1. When one takes the position that no particular form of government is set forth in the NT, then pretty much anything goes. They teach that congregations should have elders, but (correct me if I'm wrong) it seems that otherwise it is pretty flexible. So flexible that reportedly several years ago Mars Hill did a "reboot" and cancelled everyone's membership, had everyone go through some kind of reorientation class and then had everyone affirm a new statement of faith. I've seen reports that they lost about 1000 members in the process. (Again, correct me if I'm wrong about any of this.)
2. While this doesn't exactly fit with any of the usual models of church government, it does appear that this multi-site phenomenon is often closer to a diocesan model than anything else. In the vast majority of cases, the members never assemble together. (To a lesser extent one could argue likewise with regard to multiple services in a larger church.) Someone mentioned Chuck Smith/Calvary Chapel. I don't know enough about them and their Moses Model to know how much they would have in common with MH.
3. I can't recall ever seeing anything like this campaign in which public appeals are made to come under the umbrella of a certain church. In my area, there was recently a small and apparently struggling church that came under the oversight of a larger church. (This campus does have an onsite pastor and aren't simply showing a pre-recorded video or a simulcast.) I've been told that this isn't seen as a temporary arrangement either. Questionable as some of us might find that to be, it's not the same as having a campus halfway across the country. But MH didn't start out that way either.
4. Churches planting new campuses and maintaining that as a campus of the original church (instead of moving toward it being a particularized local congregation) isn't anything new, but it is becoming more common. As someone mentioned above, it is a way of creating what amounts to a franchise. The main campus maintains control instead of taking the risk of having that church particularize (i.e. become autonomous) and taking a left turn at some point. It's also a way of branding. The general public knows what they're getting with a Mars Hill Campus, a Highview Campus or whatever. It seems that most evangelicals don't have a big problem with it because they don't think the NT has anything to say about the issue one way or another. The exceptions would include folks who the multisite proponents would tend to categorize as "old time" traditional Baptists (Confessional Baptists and Dever types would be in that category for the sake of this discussion) and confessional Presbyterians.
In most cases Dr. Mohler (a member of Highview Baptist, a large multisite church in Louisville) would seem to be in large agreement with Dr. Dever. But this is one case in which they obviously disagree. If I'm not mistaken the church that Dever pastors, Capitol Hill Baptist, intentionally doesn't even have multiple services.
Edit: Here are some brief MacArthur comments on the multisite phenomenon and the implications from a pastoral standpoint
http://www.gty.org/blog/B120126
