First rule of PR: Know your audience. IMO you are marketing your site all wrong if you go after the HN/Digg/Reddit crowds, which generally tend to be more techy.

You should be hitting the websites which would want to use this service, deal sites, shopping forums, price comparing forums, etc. Attack the forums/discussion areas in those sites, which are very large. If the shoppers from those sites aren't interested in your service, then you may have a problem with execution/the idea behind your website.

Again, HN/tech crunch/digg/reddit is the wrong audience for your idea.