At a practical level, some aspects of the semantic network are removed:
1) Semantic markup helps search engines identify key content and improve keyword results.
2) Online identity is growing, and semantic markup in links such as rel = 'me' helps eliminate these things. Autodiscovering social connections is definitely coming. (Twitter uses XFN markup for all your information and your friends, for example)
3) Google (and possibly others) are starting to pay attention to microformats, such as hCard and hCalendar, to gather more information about people and events. This feature is still on the "very new" list, but these microformats are useful examples of the semantic network.
This may take some time, but there are certain potential benefits. These days, I would not put much effort into this, but it is definitely worth keeping in mind when you develop a site.
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