America Online is losing market share, and it has been losing share for years. The same is now true for Yahoo. Lycos has the right idea - it has been building a network of services that each stands on its own in the market, rather than throwing its name around. Everything else on the Internet is built on these basics. Your site offers content, commerce or a service.
Community is just a series of additional services built on content.
In the end, the content sites will win that battle, but publishers shouldn't be sanguine, as the ClickZ example illustrates. Services can trump what rival content provides, and if those providing services expand into content, they can take the market away if their content is better. When the California gold rush was over, the mining industry had just begun. When the oil prospecting at Spindletop was over, the oil industry was just being born. When the crash of 1907 took away hundreds of cereal makers, that industry was just in its infancy.