But Salesforce and its cousins will have to be extremely attentive to service issues and interruptions going forward. While the Salesforce.com outtages don't seem to have a common cause, and may be expected from a company growing as fast as Salesforce is, knocking your entire North American customer base offline, for any reason at any time is untenable -- and won't engender a lot of good will.

Apologists for SaaS point out that traditional client/server software frequently crashes and experiences outtages as well. But companies such as Microsoft or SAP don't need to worry that all of their customers will be affected by an glitch at the same time.