The secret product Facebook will announce on Monday is, in fact, its new email system, says TechCrunch's Jason Kincaid.

Given that Facebook has already replaced email for many younger Internet users--and become the "start-page" and communications hub for many of the rest--it makes great sense for Facebook to offer a full-fledged email product.

If Facebook offers a good email platform (easier said than done), the product could gradually have a devastating impact on Gmail, Yahoo, AOL, Hotmail, and other email systems.

In so doing, it could also hammer their financial performance. Yahoo and AOL, especially, generate an enormous number of page views (and, thereby, ad impressions) from their email users. As these users migrate to other platforms, they take their impressions with them.

The mass exodus from AOL Mail has played a big role in the company's financial collapse in recent years, and Yahoo Mail has begun to see the same sort of erosion. Thus far, the defectors have generally gone to Google. If Facebook's email client is strong, many of them will now likely go to Facebook.

Knowing Facebook, it will likely put a twist on the normal email experience, and the way it integrates the main Facebook service will be critical to the product's success.

See Also: Latest on the Facebook-Google-Apple War