The auto-scaling model of the cloud eliminates the need to predict fluctuating business demand. Scale your resources up or down, only ever paying for what you use.
Visitors to your website expect fast and reliable site performance. Whilst powerful centralised hosting can provide this, often large capital expenditure is required - essentially you get out what you are prepared to put in. However considering you cannot always predict a spike in demand, 100% reliability is difficult to ensure. Having to choose between overspending and under-provisioning is a classic dilemma.
Using the cloud you can avoid this scenario by paying as you go for what you use, not tying up your capital with unnecessary infrastructure and facilities. You can manage your peak loads with automatic scaling rules once your applications are deployed in the cloud.
The combination of cost and performance benefits is the reason why so many enterprises are now re-deploying many of their business critical applications into the cloud.