I recently put a lot of video files >10 GB on my 32 GB iPhone and noticed that when I sync it to iTunes, the backup process (which is the 1st thing it does) not only takes a very long time but I can see that it is eating up my disk space at an alarming rate. When I sync again, the backup eats up ADDITIONAL disk space! Shouldn't each backup overwrite the previous one, not create an ADDITIONAL file on the hard drive, wasting space?!

Is there a way to reclaim this disk space? If needed, I will have to delete the files on my iPhone so the backup is not so large but I would like to avoid this if possible. I want to make good use of my iPhone's disk space. Any help would be much appreciated.