Example here, and practically every time you see someone Famous And Important leaving a building.
I can understand print and radio media needing to get near, on the off-chance that they might ask some questions and get some answers. But you see pictures like the linked one, and it’s just a swarm of people with video and still cameras, all with the lens about three inches from whatever person. Don’t they have zoom lenses? Why do they need to get so close?
If you don’t get close, someone else will get in front of your zoom lens; and the tighter you zoom in with your zoom lens, the more magnified any jostle or shake or your camera becomes, resulting in an unusable photo.
Yeah, pretty much what Waloon said, it’s so they can get a picture because of all the photographers in the way. 
The question I have is why does the media do this to people who have no skills, no looks, no talent, and no position of importance (a.k.a Paris Hilton)?
Ok, I can see a reason for mobbing some hot actress. Said actress has the talent of acting that the public enjoys. I can see a reason for mobbing a political figure. That person is in a position of political power that has an influence on the public. I can see a reason for mobbing a sport figure. They have the talent to play their game well.
But there are some people who don’t have any of that and the media descends on them like a swarm of locusts. Come on. If I were to start going around and crashing parties, getting drunk and parading around like a 2nd rate whore, I wouldn’t get media coverage. So what does somone like Paris Hilton have to deserve all that attention?
Young, Thin, and Blonde. That’s all that counts. Haven’t you read the unwritten rules?
That’s not enough, though. She’s thin, young, blonde, and heiress to an enormous fortune. She’s like Regina Rich.
The media are swarming because we’re watching and buying and reading. If we weren’t, the media would not have the advertising revenue they need to survive. The media have a limited ability to foist someone on an unwilling public. The media can and do, however, pander to our mindlessness.