How big can an Intranet be?
An Intranet can be as big as a community of interest. Scale is an important factor in web implementation, but it has no bearing on the logical association of clients that make up an Intranet. For example, a workgroup with one web server, a company with several hundred web-servers, and a professional organisation with ten thousand web servers can each be considered an Intranet.
While nothing constrains these webs to be "inside" or bounded in any physical sense, size is a significant consideration from a network design perspective.