Google Chrome ships as a 500 MB binary on my machine, so if you're embedding a web browser, that's how much you need minimum. Now tack on whatever else your application needs and it's easy to see how you can go past 2 GB if you're not careful. (To be clear, I am not making a moral judgment here, I am just saying it's possible to do. Whether it should happen is a different question.)
I just checked Google Chrome Framework on my Mac, it was a little over 400 MB. Although now that I think about it it's probably a universal binary so you can cut that in half?
