I don’t know how long journalists have been using the phrase “on the ground,” but it seems to be more commonly used than ever before. I don’t see how it adds anything to a story. In the following examples if you removed “on the ground” the meaning would not change at all.
“… Marines saw and felt on the ground — their views on the failures and triumphs of their push toward Baghdad.” — All Things Considered , March 19, 2004 [I suppose the phrase is used here so we know the author is not describing what the Marines saw and felt at home or the office, but is that really necessary?]
“And Nadya Sbaiti says, ‘… manipulation of the facts on the ground in Israel and the Occupied Territories.’ ” –Jeffrey A. Dvorkin, Ombudsman, NPR. [I guess “on the ground” is used so we know the author is not referring to the manipulation of the facts by the media]
“West African peacekeepers who are on the ground will take off their berets and will put on the blue hats” CNN [Where else can peacekeepers be found but on the ground? Are there peacekeepers in offices?]
Edit: The article by the NPR ombudsman was removed from NPR.org.