Tumblr developer Marco Arment has, in his spare time, created two very useful Web services on his own. The first is Instapaper; it's for saving links to Web articles that you want to read at some point, but don't have time read right this moment. It's like Del.icio.us or other bookmarking tools, but without all the features you'll never use. You click a "Read Later" button in your browser's bookmark toolbar and a window pops up to tell you that — phew — the article has been "Saved!" Later, you can go to Instapaper.com, login, and find all your articles piled up. I've discovered Instapaper is best used as a way of pretending that you're actually going to read a very long article on Chinese politics or Emily Gould's essay on oversharing.

While editing administrator code today, Tumblr founder David Karp and developer Marco Arment inadvertently published private user data for 40 minutes. Karp reports on his blog that 27 email addresses were exposed. He told us that four accounts — including popular Tumblr blogs by Julia Allison and Pete Nidzgorski — had their passwords changed. Karp told Valleywag he knows who changed the passwords. "He was a registered user, so we were actually able to look up his info," Karp said. The suspected hacker won't lose his Tumblr account. "I don't think we'll be taking this out on him," Karp said.