Ticketmaster / Live Nation - Government Barriers of Entry?

I have been having an ongoing debate with a coworker regarding the tendency for monopolistic scenarios to be grounded in regulation and/or lobbying (possibly redundant), and other government intervention. He believes monopolies are naturally occurring and the consolidation of economic power must be mitigated through force. He cited Ticketmaster and Live Nation with their control through seemingly legitimate contracts between the record companies, promoters, venues and the ticketing agencies. While I understand large market control by a single player is not in conflict with libertarianism should they earn it through voluntary exchange, I am suspicious that this is the case given the terrible product they provide along with their high prices. I also know they are owned by massive corporations, which in this mixed economy, usually requires participating in the lobbying process. Does anyone have any information on this? Any thoughts?

Many thanks.