Being smart about your monitoring data collection allows you to isolate and resolve problems much faster, and with a much lower cost of ownership and overhead.
Here is an example of a company that replaced their legacy monitoring tool with AppDynamics. The environment they are monitoring is a good size, consisting of about 1,200 servers and their main application processes approximately 300,000 transactions per minute. They invested in a monitoring tool to help manage the performance of their applications which captured and stored all the data they could "just in-case" it was needed. Unfortunately this approach required an additional 92 servers to be provisioned for the monitoring tool itself, which consumed approximately 80TB of data storage per year. The increasing investments this customer needed to make in hardware, storage, people, and maintenance was too much to manage for them and they decided to look for a different approach.
AppDynamics "smart data" approach to application analytics means this particular customer now only requires two reporting servers and the storage requirements were reduced to just 1TB per year. Collecting only the data required to make smart decisions gave them both a 98% reduction in hardware costs and more effective analytics in the process.