According to this blog posting by Wired.com's Kim Zetter, Black Hat representatives said that the reporters sniffed the network to prove a point when it comes to accessing untrusted networks, and that they wanted to convince organizers to post the names of reporters caught accessing Web sites insecurely (in this case, probably the production systems of their respective publications) on the "Wall of Sheep."
In case you're not familiar with the Wall of Sheep, it's a traditional part of the DEFCON security conference, which also runs the week of Black Hat. And the Wall of Sheep is a wall where the usernames and partially-blocked passwords of anyone crazy enough to access Web sites or e-mail using the conference's free wireless access are displayed by a projector. Needless to say, you don't want to make the Wall of Sheep. And at DEFCON, you're probably wise to just not turn your computer on, let alone use wireless.
This year was the first year that the Wall of Sheep was brought to Black Hat.
And for this incident, the Wall of Sheep organizers refused to display the names and logon credentials of any reporters who were pwned.
The network facilities in the press room are used by reporters, industry analysts, and conference speakers, and were supposed to be not in play for the Wall of Sheep demonstration.
We'll have to learn more about what actually happened. But if anyone sniffed the communications of users on the network who were connecting to systems or networks -- and neither of those parties knew of the sniffing -- it's very likely a violation of federal law.