Ordinarily, one wouldn't take much notice of a gallon jug losing only a drop or two of water a day. But if you came back a year later and saw it half-empty, that would get your attention.
Such is the case with the steep ratings declines at CNN and MSNBC. A year ago, they already trailed Fox News badly -- so badly that Fox's audience in a given hour of prime time was sometimes greater than CNN, MSNBC, and Headline News (HLN) combined.
Revise "sometimes" to "virtually always." A comparison of Media Bistro's scoreboard for Thursday, February 4, 2010 to the same report for Thursday, February 5, 2009 shows stunning leakage from CNN and MSNBC. The jug is less than half full:

CNN and MSNBC both declined over 50% in the 25-54 demographic, while both networks also suffered seriously in total audience.
Much more detail is in this graphic. Some highlights/lowlights from that graphic:
While it's heartening to see steep falloffs from the fever swamp, those of us who would like to see more Americans tune into the fair and balanced reporting of Fox should not be overly cheered. Less than a quarter of those in the 25-54 demographic who tuned out MSNBC and CNN switched to Fox; barely a sixth of total viewers did so.
Where did the rest of them go? Some may have decided to tune into the evening newscasts of ABC, NBC, and CBS, as their viewership is up about 10-15% since fall of last year. The rest appear to have tuned out -- at least from television news. Unless one believes that the vast majority of the rest are actively visiting blogs and social media to get their news, which seems hardly likely, a lot of the potential electorate may simply be tuning out. This would not bode well if one believes that a highly engaged electorate is a prerequisite to turning the country around.
Cross-posted at BizzyBlog.com.