The headline on today's top story, "Google's Achilles' Heel," references classical mythology. Here's another classical mythology reference that's not mentioned in the story: Scylla and Charybdis.

In Greek mythology, Scylla was a monster who lived on one side of the Strait of Messia. A whirlpool named Charybdis was on the other side of the strait. Ships passing through the channel had to carefully steer a course between the two hazards. If they went too wrong in one direction, the sea monster got 'em, and if they went wrong in the other direction, they went down under the whirlpool.

(Still other navigational errors would result in their being stranded on Gilligan's Island. But ancient Greek legends don't discuss that.)

Reading over "Google's Achilles' Heel," I'm struck that Google is attempting to navigate between Scylla and Charybdis.The company gets virtually all its enormous revenues from keyword-related advertising. Type a search term into Google, and you'll see ads that are triggered by that keyword. Similarly, if certain keywords are present in a Gmail mail message, or on an external site that belongs to Google's ad network, you'll see ads related to those keywords as well.

That's a huge, and growing, business. But how long will that last? As our story points out, only until somebody else comes up with better algorithms.

Google appears to be aware of this, that's why it's scrambling to develop new products and services at a frenetic pace.

But in doing so, it can't lose sight of the original business.

It needs to innovate and create new businesses, while also avoiding losing sight of the old business. In other words, it needs to navigate between Scylla and Charybdis.

Read our story for more insight into the threats facing Google: In addition to excessive reliance on search advertising, there are also lawsuits, eroding public trust, lack of focus, and the competitive threat from Microsoft.

And, in other Google coverage: Google News is out of beta, and we have a review of Google Pack, the recently-released bundle of desktop software for personal productivity, security, and fun.

If today's Google coverage leaves you hungry for more, we're running another major Google story on Monday. I just read a draft, and it's a beaut; I'm eager to see the finished product, and for you to read it.

What do you think? Can Google successfully steer through the threats facing it?