The Department of Justice has a right to look into what they perceive as breaches of security, and with a fairly recent law change, they even have a right to do so without getting warrants on occasion. But (though I think that that law should be changed), it's generally been done is a limited manner, seeking out specific information on a specific individual. This just threw out a net to see what they could catch.
As far as it appears, no wiretaps or transcripts of conversations and emails were sought. But the impact is bad nonetheless. If you're an anonymous source who's considering talking to a reporter only on the condition that your anonymity will be protected, how likely are you to do so if you think the government might know you're talking, regardless of whether they know what you said?
It certainly doesn't come as a shock that government officials hate leaks and will do anything to try and stop them. But you not only expect there to be limits, but you also hope that those less-controlling will be more attune to those limits. Again, it doesn't appear that there is anything tying this to the White House, but -- a) it shouldn't occur even at the Department of Justice, b) that's too close to the Administration, and c) there was no direct order from Henry II either when he offhandedly bemoaned, "Who wouldst rid me of this turbulent priest?", but Thomas More still ended up dead.
The one interesting aspect of this particular situation, though, is the corner it paints for Republicans. Normally, they'd likely be all over President Obama for even this hint of a scandal. Except that they not only hate journalists almost as much as they hate him and have such a long history going after them, but when the original leaks occurred, they were all the president to investigate where the leaks came from. So, they're in the position of criticizing the president here and going against their true beliefs of hating the press, or criticizing reporters and supporting Barack Obama. If I had to guess, simply because they're too much on the record on this and have too long a history trying to put journalists in jail, that I think they'll fall on the side of the Administration.