<![CDATA[Prismatic wants to build a social network around all of your interests, which is actually a lot harder than it sounds]]>

There are social networks all around us these days, from Facebook (s fb) and Twitter (s twtr) to more targeted networks like Instagram and Path -- and new ones seem to be launching every week. Do we really need another one? Bradford Cross, CEO of San Francisco-based startup Prismatic, thinks that we do, and he is doing his best to create one using the news recommendation algorithms that he and co-founder Aria Haghighi…