Different scales are more appropriate for different types of applications. Some digital data layers are generated from an existing analogue (hard copy) data source. These analogue data sources are associated with different map scales. For example, local parcel data is often acquired at a 1:600 scale, while topographic maps are collected at 1:24,000. You could not use a topographic map to accurately develop a parcel data layer, as too much information (and, thus accuracy) is "lost" at the smaller scale.
Accuracy levels are often associated with scales. The National Map Accuracy Standard (NMAS) was developed by the U.S. Bureau of the Budget (1947) to standardize accuracy levels of spatial data. Thus, certain applications (such as surveying/parcel management/floodplain delineation) that require a higher level of accuracy need to be associated with larger scale data layers (i.e., 1:1,200/1:2,400) that were generated in compliance with NMAS.
Read more about Map Accuracy and Scale.
It should be noted that computer screen resolution and original data resolution are not the same thing. While GIS software will enable you to zoom in (and out), altering the scale at which you visualize the data, the scale (and accuracy) at which your source data were created does not change (no matter how far you zoom in!). The accuracy of what you produce in a GIS is limited by, among other things, the scale at which your original source data were captured, which is why it is so important to document this in your metadata and report it in any products (maps, reports, etc.) you create. For additional information, refer to National Map Accuracy Standards.
