Big media companies such as Viacom, News Corp. and Time Warner are so anxious about missing online opportunities that they are moving some of their most valuable content online even as that move puts longstanding business relationships at risk. The Wall Street Journal reports on the lurching and sometimes frenzied acquistions of media companies that see traditional sources of revenue diminishing and hope to fill void with Internet ventures. The Journal reports that some of those media companies are treading a fine line: hoping to extend their existing businesses onto the Web without cannibalizing their traditional audiences. So, for instance, Viacom’s Nickelodeon cable-TV channel is limiting the amount of television content it puts on its Web site so as not to undermine the TV channel. Read more.