Yesterday Dropbox announced that they will close their Mailbox app and service in February.1 This is yet another case of a big company acquiring an email-client startup and shutting it down, and it doesn't surprise me. Nobody wants email clients (except for me and my girlfriend), because GMail's web interface is good enough or even great for most people. Writing an email client is deceptively hard, and yields relatively small payoff. Also, Dropbox needs to concentrate on its collaborative tools efforts in order to be able to compete with Google Drive (a game it's late to, if you ask me) and now that Inbox copied most of Mailbox's features, there's simply no point in trying to win GMail's userbase.
The only thing that bugs me with situations like this, i.e., when a big company decides to shut down a niche product (especially a product of an acquired startup), is that they don't release the technology as an open source project. What could possibly hurt Google to release Sparrow's source to the community, or Dropbox to do the same with Mailbox? We'll never know I guess.