All of those examples you give are a) easily identifiable (e.g you are transmitting on a particular frequency) and b) scarce due to very high barriers to entry (e.g betting a power utility).

Web sites are different. Facebook is just one end of a spectrum of thousands, perhaps tens or hundreds of thousands of electronic destinations that come and go, and cost a few bucks to operate.

Regulations aimed at Facebook would potentially end up targeting every web site with user generated content.