It's not clear why anyone should be surprised that Gmail, Amazon.com's cloud services, Salesforce.com, MobileMe, or Netflix have periods of instability or downtime. These services are not promising five-nines of uptime, and they are dependent on complex code and a vast network "tubes," as the beleaguered Sen. Ted Stevens has said, to deliver bits to users. Services such as Twitter have set a new standard for unreliability, making the other cloud-based services look good in comparison despite their outages.
The much-ballyhooed cloud from which Web services emanate is inherently unstable and prone to odd behavior from any number of causes. At the same time, the Internet overall is incredibly robust and redundant. You just don't want to be caught at the intersection of some errant configuration change or badly behaving router. In the case of a Gmail outage, you need to have alternative e-mail services that capture messages from multiple sources to stay afloat.
Over time, the complex network systems underlying the Internet will become more reliable, but don't count on the Internet of 2008 or even 2015 to be operationally flawless. If you are not careful and proactive, the cloud will rain on you without warning.