I was really skeptical at first, but they're legit. It's a non-profit that's been around since 2009, based in Berlin. Have a look at their blog, you'll find project updates, the financials are broken down by expenditure and much more. Finally they're getting some spotlight with this recent TechCrunch article and their big efforts on Social. What really hooked me in is that they signed a legal contract binding them to the not-for-profit purpose forever - more on this. Edit: about Mr. Oliver (love this guy) he is absolutely correct, but he is referring to for-profit companies that pollute and then plant some trees to pretend like they give a damn. Ecosia is a not-for-profit whose purpose is to plant with a purpose, meaning they reconnect forest patches that have been split, they return livelihood and wildlife to areas that have gone through droughts and seen increased poverty etc...