Take a look at this project which is similar to yours (not mine btw): http://annotatr.appspot.com/
Annotatr looks somewhat similar yes. They too have some issues with getting to critical mass, but you have to start somewhere. I have to look into integrating more services into Tiris (pubget, citeulike, mendeley). I think the biggest difference will be when I implement the embeddable commenting system, which should enable easier access to Tiris.
About dropping me a note, hmm, yeah, that could be a bit difficult. Sorry about that. If you come to my site http://www.juretriglav.si - there is an email link right at the bottom of that page. Sorry I have no better way.
Off-topic: How does HN usually solve this lack of PM issue?
Many people put their email in the About field of their profile. You can obfuscate it if you wish, or just trust your spam filters.
For example, you can comment on this paper right here: http://tiris.org/papers/15
If you are a user you can then follow what goes on with the paper (new comments, tags, etc.), you can follow the user who submitted it, seeing as he is likely to have similar interests, you can follow the tags the paper is tagged with and so on.
It is dream for Tiris to be embeddable into various scientific sites (blogs, project pages, etc.), with a system similar to Disqus, but with a knack for science (for example, latex is supported with $$ math $$).
We're slowly but surely getting there, if there is anyone reading this who feels passionate about opening up scientific communication, drop me a note.