not been wholly kind to Second Life, and those circumstances don't seem finished just yet. The Emerald client, one of the most popular third-party viewers -- estimated to be used by as many as half of all players -- has fallen out of favor with Linden Labs and is no longer an officially endorsed option. Scott Jennings has posted a full rundown of the client's history, charting its progress from the earliest inception of the project to its current status of having fallen from grace.
The short version (or as short a version as you can get for drama four years in the making) is that Emerald's coders included some rather... hack-tacular backdoors in the client's coding. This is a downside for reasons that should not need to be specified, but does add up to some major problems for the large playerbase still using Emerald. Second Life has had a hard time getting its users to switch to the 2.0 viewer, and about the only upside may be that the removal of Emerald will change that... but the overall drama isn't going to be kind for either the Emerald project or Linden Labs itself.