I'm personally not saying that excuses it, but I've once read that it was an absolutely conscious decision by Apple to put the port where it is.
A lot of people tend to simply leave the mouse plugged into a cable when using it, even once it's charged. Apple is famous for the image that they would like their products to convey. They don't want people leaving the mouse plugged in because it's convenient or they're unable to act on a month-long warning. They want to force you to use the mouse as it was designed -- wireless.
I'm not saying it's good, I don't have one myself and I plainly don't like the ergonomics of it. I like the look and I think I would be able to work around the port-location constraint, but it just doesn't feel nice to hold.
