Why does the Network icon in the Finder sidebar in Lion have no function on my Mac?
~/Library/Preferences/com.apple.sidebarlists.plist

In Terminal, run the following command. You should find the word Network mentioned at least once in your .plist preference file: 

defaults read com.apple.sidebarlists | grep Network

Applicability

As I can't drag Network to my Finder sidebar — and as sidebar takes a different approach to showing shared items — I guess that: 


in Lion, Network is no longer applicable in the FAVORITES part of the sidebar
maybe for you, Network was amongst sidebar favourites in a previous version of the operating system. 


Removing unwanted items from the property list

Probably easiest with Xcode. 

If you don't have Xcode, then use TextWrangler or anything that's capable of editing this type of property list. 

Identifying items in the .plist

Xcode views of the property list:




A TextWrangler view:



To view Network, with or without the sidebar

⇧⌘K

In the sidebar


show SHARED
click All… 




If the option 'All…' does not appear

First try removing, from the property list, unwanted or redundant items relating to Network. 

A guess: it may be necessary to quit Finder, or log out, before some types of change become effective. 

If following removals and a log out you find that SHARED is still without All…, consider asking a separate question.