It is in fact pretty hard :) We are working on content summarization too, with a Chrome extension that lets you read a human written summary of Hacker News frontpage links. Writing the summaries and making sure you're up to date takes time. You need to make sure you stick to the author's point of view, that you really understand the article in depth and groked the key points. Of course it depends on the article you summarize but I can spend a good 30 minutes on one article by Paul Graham or Mark Suster.

PS: the chrome extension I'm talking about is here: https://chrome.google.com/webstore/detail/tldr/ohmamcbkcmfal... (same one czzarr is referring to)