What is entrecard?

According to entrecard.com introduction:

Entrecard is a free blogging network that truly brings visitors to your blog. By joining our network, you can earn Entrecard credits which allows you to display an ad of your blog on other blog sites within our Network. Sign up today and see why tens of thousands of bloggers are using Entrecard!

Very interested in. Their introduction are attractive. But like in real world, you have to work hard in order everyone knows you. Like other SEO techniques, you have to make friends, drop cards, advertise... to let your site stay in the first position in search result. If you are on top, you will be easily get more traffic. If not, no one visit your site.