Touted as a replacement for email (amongst other things) when launched, Google's Wave application is closing down. Matt Asay over at the Register has a good analysis. There is no doubt in my mind that Google can afford a number of failures as it innovates, but this combined with the recent Nexus One online shop failure might be signaling the start of a trend.
Updated 2021 : note that the above post was originally published in 2010, but is left here for archival purposes. The original article from 2010 on CNET is gone, so I have updated the link to point to the Wayback Machine backup.