NPR has an online audio story on "Photographers as Security Concerns:"
Morning Edition, June 16, 2005 · Photographers across the country have complained of getting harassed by law enforcement officials citing security concerns since the September 11 terrorist attacks.
There are good links to information and resources on photographer's rights on the right hand side of the article page.
This does seem to be part of a general trend towards paranoia. The NY Times reports today (2005.07.04) that "Journalists say threat of subpoena intensifies:"
In the last year, more than two dozen reporters across the country have been subpoenaed or questioned about their confidential sources in cases before federal courts, according to the Newspaper Association of America. Paul J. Boyle, senior vice president of the association, said he believed that "the filing of subpoenas, as well as the letters and phone calls that media companies receive from prosecutors and civil litigants, is on the rise."