With Kennedy came the rise of mass-media, especially with how photogenic the First Family was. At the time, however, news outlets cared more about discretion than ratings. Times changed with Nixon, when every little indiscretion was rooted out, cataloged, and pinned like butterflies to billboards for all the world to see. And it's been that way ever since.
Add to that stew the bloggers. You have those deeply interested in how things work, those grinding an axe, those desiring to re-write history, others with no other purpose than mischief, and some more wanting a bigger name in the hopes of being taken seriously. In some cases, bloggers broke stories and spread them like gasoline fed wildfires long before the mainstream news organizations had even gotten their boots on. And that's the new dynamic: journalism sans responsibility.
What was once kept private is now vaunted in public, with some doing the reporting without oversight or standards.