I am not interested that much in web icons and usability but rss syndications icons are sometimes a bit too... different, as workbench points out:

Considering the number of ways that web publishers show their readers they offer feeds, it's amazing we've gotten that many:

In an effort to make the concept of syndication easier for mainstream users, the next versions of the Internet Explorer and Opera browsers will identify RSS and Atom feeds with the same icon used in Mozilla Firefox. Since the market share of these browsers tops 95 percent, the icon will become the de facto standard for syndication overnight when the next version of Microsoft Windows comes out later this year.