Funny you should ask. When we launched the Postable address book we had no idea it would take off the way it has. It just fills a very specific niche of making it easy to collect friends' mailing addresses. And then beyond sending the first batch of cards, it becomes an indispensable tool for keeping up with important occasions in your friends' lives. There are many copycats but none of them quite capture the magic of ours. And it's free ;-)