Spaces or Tabs?
In this day and age it seems silly to get into a discussion about whether your companies coding guidelines should have a section mandating either spaces or tabs for indents. Tabs are clearly more flexible, but I really don't think it matters at all; people can easily read code that contains spaces or tabs.
But, Microsoft has departed from what seems to be the rest of the world and is mandating spaces in their new Microsoft Source Analysis Tool for C#.
Word is that an update will not only mandate spaces but mandate 4 for indents.
Again, I don't think it's much of an issue; except Microsoft Source Analysis Tool for C# doesn't offer a rule to mandate tabs over spaces. They're not providing a tool for organizations to use to enforce local coding guidines, but providing a tool to mandate Microsoft's coding guidelines.
The tool can be downloaded here and a discussion on tabs can be found here.