It's possible, but the wider the lens, the more magnification when you reverse it, and you don't really get anything in focus. Well, you can, but the exposure would be extremely dark because you'd have to shove your subject pretty much into your lens. Essentially, if you think of it like, the wider the lens, the smaller the image, but the bigger the lens, the larger the image, as you literally are reversing everything.
The 70-200 is a better option to use. It's still a very small distance between the lens and subject, but a lot more practical.
70mm is practical. I can do so on my 24-70 II and 70-200 f/4, but 100mm reversed would be ideal (not just because it's the same focal length as Canon's actual macro lens). http://www.digitalrev.com/album?id=7093364
Here is some examples of what I did with my 70-200 f/4 IS and 60D. It's a very difficult to focus. And you can only focus by moving the camera along with the lens back and forth.