When Twitter acquired the blogging platform Posterous last year, it said it would be keeping the service alive — but now it's time to turn off the lights. In a blog post today, Posterous announced that the service would be shutting down on April 30th so the team could "focus 100% of our efforts on Twitter." At that time, users' Posterous pages will cease to exist. Fortunately, the service released a backup tool last December, so if you've been documenting your life on the platform, you'll have until the end of April to download your content. The post points out that both Squarespace and WordPress have tools that will let users easily move their Posterous content over to either service.