I get notices all the time from salesforce.com about "scheduled downtime". This time the email describes a six-hour window this Friday night during which salesforce.com may not be available.
I want to use salesforce.com to capture requests for customer support but those come in at all hours of the day, especially since my business is global—my customers are all over the world. There's no way my support page can be down regularly for hours at a time.
If salesforce.com wants to make itself part of the infrastructure of not only 9-to-5 businesses with American customers but also 24-by-7 businesses with customers all over the world, they're going to have to change something fundamental about their operations.
Update: In the comments, Scott Jorgensen from salesforce.com points out that the Web2Case feature will queue new cases until the maintenance is complete. That's very good to know. I assume the same is true for Web2Lead, but what about other customer-facing features like the Self-Service Portal?