I had never heard of it, but I googled it and came up with some things that would concern me. It sounds like the site downloads lots of stuff on your computer including a toolbar, which would allow them to monitor which other sites you see. Here are a couple of sites that discuss it. While I was just trying to read about it my Norton system when nuts, and it still blocking things. I would stay away from it!
What is zwinky and is it appropriate for a 10 year old girl? - Yahoo! Answers What is Zwinky?? and is it safe for your computer? - Yahoo! Answers