Search engine optimization is a critical aspect of site design. While its complexity far exceeds the scope of this blog, it is worth mentioning as it regards the design of the content tree.
Two rules of thumb are useful here: 1) Search engines attribute semantic weight to content hierarchy and 2) Shallow structures may be more optimal than deep structures.
Addressing point 1), a search engine will treat /Products/Shirts/Men/Knit.aspx as more semantically rich than /Foo/Foo/Foo.aspx. Each level in the hierarchy is considered significant when interpreting the meaning and categorization of the link. Fortunately, Sitecore is designed to facilitate this kind of content organization; Sitecore’s “friendly-URLs” allow for search-engine friendly paths.
Regarding point 2), content in shallow branches may be deemed more significant than content in deeper branches. For example /Products/Shirts.aspx may be considered more relevant to a site than /Products/Shirts/Men/Knit.aspx. Most of the time, the need for content organization may trump this consideration. However, addressing categorization through metadata may be an alternative to expressing categorization through hierarchy.