David Corn’s first-hand experience has him wondering over at Mother Jones:

Is the McCain campaign screening reporters [on its conference calls with aides and surrogates], and, if so, on what basis? A reporter for a progressive media outlet says that he has tried at least half a dozen times to ask a question on a McCain conference call and has had never been selected.

The same has happened to me.

Corn presents several anecdotes like the following:

During a June 27 McCain campaign call with former Republican Massachusetts Governor Jane Swift… I raised my hand, electronically. Two reporters were called on—one from AOL News, the other from the Tampa Tribune—and then the McCain aide hosting the call said, “Seems we are out of questions,” and ended the call. My hand was still up.