I think a site organized around "links to papers" would have an even harder time gaining critical mass because people find out about papers in so many ways (wor

I think a site organized around "links to papers" would have an even harder time gaining critical mass because people find out about papers in so many ways (word of mouth, conferences, blogs, arXiv), and the "best" ways to find out about papers that you'd then devote a long time to reading usually need serious motivation (great talk, met an author, know you need to learn a technique) rather than a random link.