Are Late Night Talk Shows Obsolete?

This is the 50th anniversary of Johnny Carson taking over the Tonight Show. Steve Allen and Jack Paar made the show an important part of the television landscape, but Carson turned it into an American institution. Even after his departure, the next generation of hosts -- David Letterman, Jay Leno, and Conan O'Brien -- maintained a sense of relevance for the slot. But with the proliferation of entertainment and media options, have these programs lost their place in our culture?

For the last bunch of election cycles, appearing on them was essential. Bill Clinton playing the saxophone on Arsenio is as iconic a political broadcast moment as the Checkers speech or the Kennedy/Nixon debate. For comedians, playing Carson was the gateway to a career. But the stature seems to have been lost.

Is this the case? Are late night humor/interview shows no longer the cultural powerhouses they once were? If so , why? Is it the hosts? the writing? Is it the technology? the times?