“There is supposed to be this Chinese wall at the company,” says Mitchell Frank, who books shows for a Los Angeles club, Echoplex. “But really, what is to stop them from mining all the data that I collect?”

If the merger presents so many potential hazards, why did the Justice Department approve it?

Several people familiar with the negotiations inside the department said that officials didn’t think they had much choice. According to Jim Hurwitz, a former Federal Trade Commission lawyer who wrote a paper for the American Antitrust Institute arguing against the merger, Live Nation told the government that it was going to exit the ticketing market no matter what happened with this deal and that it would enter an informal alliance with Ticketmaster if it wasn’t allowed to merge. On the other hand, if it was allowed to merge, the government could exert some control through a consent decree.

In other words, Mr. Hurwitz explained, the choice presented to the Justice Department was this: either let us get married and have a say in our union or try to stop us — in which case, we’re just going to start seriously dating. “My sense also is that Justice was worried about its prospects if it went to court, and it didn’t want to lose its first major case,” Mr. Hurwitz says.

Ms. Varney of the Justice Department has disputed that notion, saying that it would have litigated if it hadn’t won the concessions it wanted.

NOW that Live Nation Entertainment is a reality, how does it intend to grow? Mr. Azoff and Mr. Rapino are still coming up with answers. They want to improve Ticketmaster’s e-commerce site and look for ways to sell merchandise, fan club memberships and so forth to people buying tickets. The two executives talk about new pricing models and a better fan experience.

Potentially, these changes are revolutionary. For years, neither promoter nor ticketer has considered fans as the first priority. Ticketmaster’s most important clients are venue owners. The promoter, of course, worries foremost about the artist. If you’ve ever attended a concert and felt treated like an afterthought, now you know why.

But as Live Nation Entertainment tries to create this fan-friendly concert experience and improve its margins, it has tough trends to fight. The number of new bands with arena-packing power is dwindling. The company has made few inroads in hip-hop and rap. We live in a world of downloadable singles, but albums and artists’ repertoires are what traditionally sell big tours.