People click on it, they can send you a message and YOU never reveal your email address. It reduces spam, guards your privacy and keeps you contactable. This is great for websites as well if you don’t want to put up an email link. These days Spam Spiders are sucking down any and all e-mail addresses they can find, auto-adding them to their spam-lists, so this is a great way to avoid that.
They also offer code to embed the links with widgets for blog posting, which I will likely do myself very shortly.