There are reports of a Ticketmaster-Live Nation merger.  Billboard news does a nice job of summarizing the potential effects:

The two strategies of Live Nation and Ticketmaster Entertainment have been quite similar: vertical integration, direct connection between fans and artist, bundling of content and tickets, and harnessing of the secondary market and the revenues produced therein.

The potential merger would leave the other players in the music business marginalized. While there is also talk that the second largest promoter, AEG Live, has been under the acquisitive eye of both Live Nation and Ticketmaster, independent promoters have to be worried that they will be on the outside looking in.

Agents should be concerned that their relevance with artists could be diminished when the keys to the vault are held by one powerful entity. With live music already the most reliable income stream for most artists, labels would have even less influence and would move more solidly into roles as distributors and, to a lesser extent, marketers.

I think I speak for all music fans when I say I hope this merger does not go through.  Competition in this space is a good thing, and the last thing we all want is even higher fees for purchasing tickets online (which are already too high as it is).  This potential merger would allow this and other various pricing concerns to arise because one company would be holding way too much power in the live music industry.