Last week, we mentioned that Vladik Rikhter used Google AdWords to max out his Dropbox account with all the space he could get from referrals for a fraction of the cost required to upgrade his account by using Google AdWords. Many of you have already done the same, but some of you told us you didn't want to spend any money at all. Well, here's how to get an additional 8GB for free, using AdWords credits and smart keywords. More »