This is one of the photos sent around by an outraged citizen to demonstrate cyclists failing to share the road in Montgomery County. It's part of the reason there has been so much discussion about MacArthur Boulevard. I don't believe this is a photo on MacArthur, btw.
Anyway, two thoughts
1. It's entirely possible that the one cyclist who is not on the shoulder is passing the other cyclists or is drifting back after his turn in the front. Passing is an acceptable reason to be side by side, since it's very difficult to pass without doing so. I can bunny hop, but not enough to pass to another rider.
2. These cyclists are pretty close to the next car, so it isn't clear they're keeping anyone from getting anyhwere.