Hi, I'm one of the developers of annotatr.<p>First of all, it's great to see people having a look at it and offering encouragement and constructive feedback. Thanks.<p>Annotatr was more a proof of concept and fun hack than anything else. While Bosco and I did want to offer an alternative to existing commenting systems for scientific papers (Nature, PLoS, CiteULike, etc.) we also realised that a big difficulty is getting continued engagement.<p>Some time after we put it up, I adapted annotatr and turned it into mldiscuss, a site for commenting on papers from ICML 2010:<p><a href="http://mldiscuss.appspot.com/" rel="nofollow">http://mldiscuss.appspot.com/</a><p>Before, during, and after the conference this site had quite a bit of activity but has since died off. I guess the lesson here is that a narrow focus (a single conference) works better than a broad one (scientific papers) -- at least in the short term. I'll likely extend mldiscuss for this year's ICML to see if it can pick up a bit more momentum.