Ask HN: What would be the ultimate YC mash-up? Dropbox + Posterous ?

So I can't help but be blown away by all of the innovative start ups that YC births and it got me thinking... what would the ultimate YC mash-up be if you could combine a bunch of their sites together? Dropbox + Posterous = Automated blogging via dragging textile documents into a Blog folder? What's your suggestion... be creative!