Google introduced a new concept to Google Wave–“following” waves. Now, clicking on a public wave no longer causes it to appear (and stay) in your inbox; you have to explicitly choose to “follow” the wave.
When someone adds you directly to a wave, or if you contribute to a wave, you will automatically be following that wave. When you see a public wave that you would like to get updates on, you can chose to follow it by hitting the follow button in the wave panel toolbar. You can remove these waves from your inbox by hitting the “archive” button, but when there is an update they will pop back in. You can switch between following and unfollowing a wave as much and as often as you like.