This was on yahoo, and looks like a cool idea,

I get many spam a day. Basicly, there is a link to a site, and for someone to get your e-mail, they have to look a the screen an type what they see in a box. I have done this on othe sites, but did not understand why, until now 

here is a link to the article on yahoo

http://tech.yahoo.com/blogs/hughes/26347

Here is the text

I'm always amazed at how many people volunteer their email address on forums and comments sections. I suppose no one told them spammers use programs that crawl the Web in search of email addresses, or perhaps they just don't care. As a site owner, I often hesitate about posting my email address publicly, but sometimes it's inevitable.

I've used different tricks to deter spammers, like using graphics, contact forms, or spelling out the entire email address (yourname [at] yahoo.com), but somehow, those accounts still manage to get spam. You're probably familiar with CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) since most websites with logins and forms use them, but until now I haven't seen one for individual email addresses.

The folks at Carnegie Mellon University have created an application called Mailhide to help you hide your email address. Users have to enter their email address and copy a piece of code that displays a partial email address (yah...@yahoo.com) wherever it's posted. If a person really wants to find out what the entire email address is, they'll have to solve one of the two CAPTCHAs the application displays. HTML code is also provided for website owners.

The words can be hard to read, but once solved, the visitor is taken to a page that shows the complete email address (here's an example). It's a bit tricky, but it keeps spammers from collecting your email address.

Best Regards

Dave