Seeing news articles with headlines like "Salesforce.com suffers another outage" can be disconcerting, but I think somewhat expected given the complexity of the latest Winter '06 release. The high expectation of many Salesforce customers demonstrates 2 things:
1) CRM has definitely crossed the chasm and is well into the late-majority consumers (aka Conservatives) who place increasingly more value on service levels and price.

2) Computing has truly become a "utility" much like power and gas. An outage of 4 hours or 4 minutes does not go unnoticed.
As with other utilities, it will take time to build and harden the infrastructure. It has taken over 100 years in the U.S. to develop a power infrastructure reliable enough to support computing and the Internet today. I don't expect it will take another 100 years for utility computing to be as stable, but we truly are in the infancy of this model.
The Salesforce.com outages also get me thinking about the value of having a separate customer portal that is integrated with CRM but separately hosted. When these outages occur, our i-Dialogue customer portals for Salesforce continue to provide customer self-service features and broadcasting email.
As a backup option, we've been able to keep our customer data synchronized with the portal (requires Enterprise Edition) and manage leads and contacts directly through the portal interface when its convenient. But we prefer to keep Salesforce.com as the master record.