Google Wave once looked like it could become Google's next big thing, but in the end, the service was too complicated and never developed enough of an active following. Just a few weeks after coming out of beta in August 2010, Google announced that it would stop developing Wave. Since then, though, Wave was still available for new users and there was still some limited activity on the service. Starting today, however, Wave is moving one step close to its grave as waves are now read-only, just as Google announced back in November 2011.
Maybe Wave' most lasting legacy (besides the infamous 80-minute demo at Google I/O 2009) is that it, at least according to Google's own story, taught the company quite a few lessons it incorporated into its far more successful Google+.
When it was first unveiled, Google called it an "unbelievable product." Sadly, users never quite warmed up to the service and the core team that was behind it is actually now scattered among other Silicon Valley companies, including Facebook.