SharePoint:Administrations concepts and limits

I frequently get asked for SharePoint scaling limits so I though I would blog an entry I can refer people to.

First an extract from the Capacity Planning section of the Windows SharePoint Services Administration guide which answers general WSS limits questions:

None of these are hard limits enforced by the system. They are guidelines for designing a server that has good overall performance.

• Site collections (Database scope) 50,000 ... Total throughput degrades as the number of site collections increases.
• Web sites (Web site scope) 2,000 ... The interface for enumerating subsites of a given Web site does not perform well much
  beyond 2,000 subsites.
• Web sites (Site collection) 250,000 - You can create a very large total number of Web sites by nesting the subsites. For example, 100
  sites each with 1000 subsites is 100,100 Web sites.
• Documents (Folder scope) 2,000 ... The interfaces for enumerating documents in a folder do not perform well beyond a thousand entries.
• Documents (Library scope) 2 million ... You can create very large document libraries by nesting folders.
• Security principals (Web site scope) 2,000 ... The size of the access control list is limited to a few thousand security principals, in other words users and groups in the Web site.
• Users ( Web site scope) 2 million ... You can add millions of people to your Web site by using Microsoft Windows security groups to manage security instead of using individual users.
• Items (List scope) 2,000 ... The interface for enumerating list items does not perform well beyond a few thousand items.
• Web Parts (Page scope) 100 ... Pages with more than 100 Web Parts are slow to render.
• Web Part personalization (Page scope) 10,000 ... Pages with more than a few thousand user personalizations are slow to render.
• Lists (Web site scope) 2,000 ... The interface for enumerating lists and libraries in a Web site does not perform well beyond a few thousand entries.
• Document size (File scope) 50 MB ... The file save performance degrades as the file size grows. The default maximum is 50 MB. This maximum is enforced by the system, but you can change it to any value up to 2 GB (2047 MB) if you have applied Windows SharePoint Services Service Pack 1.