Initially the Google Wave team supplied mute and unmute buttons to the toolbar, but recently they swapped them for Follow and Unfollow buttons. No, they didn’t just swap names, they changed functionality as well.
Before the feature change especially public waves could fill and clutter up your Inbox quite easily. All you needed to do was open up a wave and GW would list it on top of the box on every future edit, whether great or small.
I guess the GW developers underestimated the popularity of public waves, but luckily they know better now. If you open a public wave today, it won’t be listed in any folder, unless you specificaly order this by clicking the Follow button.
The swap makes the Archive and ‘Mark as read’ options in saved searches less useful. They came in handy to get public waves pass Inbox, but from now on these waves are unfollowed by default. While it is also not very likely that you want to automatically apply archive and read options to waves that you participate in, I expect the search options to be removed from the save search box one of these days.