Note that the first two are regulations designed to encourage competition and enforce a clear separation between industries. The last one is the rectification

Note that the first two are regulations designed to encourage competition and enforce a clear separation between industries. The last one is the rectification of an externality. Perhaps this suggests a useful principal for government regulation: regulations that promote competition and divestiture, or that force companies to bear the true costs of their actions, are good. Regulations meant to mandate a specific way of doing things are bad, and should instead be structured so that they incentivize entrepreneurs to find the best way of doing things and allow them to bring it to market. Regulate market structure, not markets.