This has happened to me! I was 'robbed' by a fake ebay site. They asked me to update my information and I, an avid ebay user, thought it was legitimate, but it was a fake site. Long story short gave them my credit card info and they had a shopping spree :(. Not a fun mess to figure out. Thought I would add on to this list on how to prevent incidents like this, while it is already very good advice thought my personal experience might add something to it :) So this site I used to figure out good signs and avoiding situations like this... click here
This site offers helpful links to get your money back
Hope this was a useful add on! :)
And I would also like to say internet commerce is still my favorite way to shop as it is easy and sometimes cheaper, so my experience hasn't stopped me just helped me open my eyes a bit.