The answer to that question was once easy. Until the Internet, journalists were typically attached to an established organization that could afford to own and run a newspaper, magazine, radio or TV station, TV network, or cable news outlet. Their credibility was both individual and institutional.
For all of its flaws, and despite often high entry costs, this marketplace of ideas has flourished. Journalists know that transparency and fairness in how they cover the news are critical.
But in the Internet age, the cost of distributing news has become minimal. Almost anyone can set up a web log ("blog") or send a mass e-mailing, and present themselves as someone who surveys the public scene and presents "news." Some of these lone-wolf reporters are a refreshing challenge to the usual pack journalism of old media. Reputable reporters hear the howl and see if the yapping is worth pursuing. They benefit from the range that bloggers offer.
Some of the best-known bloggers are investigative diggers. But can they be more accurate and neutral than traditional media? The bloggers who discredited the CBS News story last fall about George W. Bush's National Guard performance show this new breed of reporter can provide a valuable service - though reliability over time is a higher standard that will ultimately separate the good from the not-so-good bloggers.
Many of the overtly political and single-issue bloggers operate without much of the same editing as the old-style media. Their "news" often carries the kind of assertive, one-sided tone too often found on the Internet.
Blog reporters raise difficulties for newsmakers, who must decide if a blogger is a legitimate journalist and then figure out what public is being served. Washington is only slowly making up its mind about bloggers.
The White House, for instance, which has remained open to credentialing many types of reporters over many presidencies, recently gave its first credential to a blogger - Garrett Graff of the blog Fishbowl D.C. On Capitol Hill, the association of correspondents covering Congress - a jury of peers - that approves credentials has admitted a number of bloggers.