It's definitely not easy to do at scale, if possible at all. I'm still in the early stages with the product, so at this point (and with this particular type of product) the personal, un-scalable approach makes sense. The style of email that I sent to Ryan, and the one that I describe in the post that he links to, is only for people that are arriving through 'warm' connections (e.g. a colleague told them about the site), versus arriving through twitter, search, etc. For completely cold connections, I use a slightly less personal approach. I shared a post about that here last week, and there were some great comments - http://news.ycombinator.com/item?id=4527094. That method still requires some effort from a real person, but doesn't include any actual 'research'.