Y Combinator-funded Posterous had its time in the sun and now it's being absorbed by the biggest player in the microblogging market. The simple sharing service struck a chord with many of Silicon Valley's elite, but it never managed to make a major dent in a field already dominated by the likes of Tumblr and its now owner, Twitter. The teams from Posterous will simply shift over to products at its new parent company and let their creation die a slow and likely unspectacular death. There are no concrete plans to retire Posterous Spaces just yet but, should that day come, we've been promised plenty of warning and instructions for backing up your content. Now we'll just have to wait and see what "key initiatives" Twitter has in store for its new employees.