You know what these three megacorporations have in common? They all thought they could get rich by acquiring other media companies.
Canwest was still paying off the debt it took on when it bought the Southam newspaper chain (which includes my employer, The Gazette) when it decided it needed more cable channels and acquired Alliance Atlantis. This gave them channels including Showcase.
Bell Canada responded to Canwest's consolidation by planning a megacorporation of its own. Bell acquired CTV and the Globe and Mail and eventually most of CHUM's assets. In exchange for the latter, BCE sold shares in the company to the Ontario Teachers' Pension Plan, Torstar and the Thomson family, and BellGlobeMedia became CTVglobemedia.
A lot of Rogers's acquisitions have been in the form of CTV's sloppy seconds (oh wait, can I not use those words?). This includes Sportsnet, which CTV had to dump when it acquired TSN, and City TV ($375 million), which CTV had to dump when it acquired CHUM. It also acquired the Blue Jays, Fido, as well as specialty TV networks and radio stations within the past decade.
I'm no financial expert, and I don't have a very clear idea of the balance sheets of these three companies, but this is a really bad time to have debt, especially risky debt (say, holding a bunch of assets in an industry that might disappear entirely in 10 years). The economic downturn that the mortgage debt crisis precipitated is certainly affecting these companies and worrying their management, but I think the debt problem is more significant here than the advertising or subscription revenue problems.
Perhaps this might serve as a warning that consolidation isn't always the best way to go.
Or perhaps not.
UPDATE (Dec. 9): The New York Times, which I can only assume got the idea from this blog post, has a similar analysis of U.S. newspapers (though in that case, it was taking on debt to acquire other newspapers that got them into trouble).