The graph that accompanies a Pew Research Center survey on media credibility released Monday shows blue lines heading south: Now just 29 percent of Americans surveyed believe the media gets the facts right, and a scant 18 percent think news organizations are truly objective. While “Public Evaluations of the News Media, 1985-2009” does not focus on technology’s impact on media, those downward trends may intersect with rising chart lines for the use of Web sites and blogs as news sources.