Planning is essential, but statistics such as average daily volume are rendered useless by enormous, temporary spikes in demand. Many of us still remember the days when mainframes ran the business world. Companies on the Internet find that laughable. It's as if someone were to suggest hiking through the Amazon rain forest with one six-ounce bottle of mosquito repellent for a hundred people. It's not going to be enough.
Technology is only half the battle.
Operational problems result from not having a datacenter mentality. But at some point they have to look at what they've got and where they're going. Architectural problems often result from not really having one in the first place. A lot of companies just start building the way a craftsman might build a table without a drawing. They don't feel they have the time, or the need, to sit down and do a detailed analysis and really map out the infrastructure they're going to need.