Imagine searching while simultaneously sharing your searches with thousands of people. Now, imagine the amount of insightful feedback and extra information you may discover from those people.
I think you could increase the usage of your site dramatically if you featured a simple, single example of a use case on your homepage which highlights the sites benefits.
E.g. if I search for a particular camera brand, how will your site be a better experience (for me as a user) than simply doing the same search through Google without using your site?
Currently, it's not possible to see the benefits, features or example usages of the site without first going through a sign-up process.
I'd make these small improvements and seeing any effects before deciding to move on.
1) Google's Experimental Search: http://www.google.com/experimental/a840e102.html. They tried making it the default behavior and no one used it.
2) Facebook: you already have a captive audience to ask for advice on non-timely questions.
3) Delicious: people already save and comment on their search results (the parts of the results they care enough about to keep around).
4) Springpad, Evernote, etc: bookmarklets & cross-platform apps let people save links, web pages, and just about anything else.
5) Instapaper, etc: save content for later.