Bookmarks has been a missing feature in the iTunes Store. Maybe it can make it to the iTunes plugin? If you think it's feasible I'll put a request at github.
In the meantime I've found a workaround. Copy the link from an iTunes item, change http to itms (you can also omit the country code), make a script, put it in ~/Library/iTunes/Scripts/Bookmarks/ and assign a shortcut in SysPrefs. --http://itunes.apple.com/us/genre/books-fiction-literature/id9031?mt=11 *open location*"itms://itunes.apple.com/genre/books-fiction-literature/id9031"
