It's not really a big deal, I have a charger at my desk for my phone. So once every 3-4 weeks, I plug in the mouse when I leave. It's never run out of battery when I wanted to use it.
i think they wanted to specifically make sure people don't use these with wires attached. Apple HATES wires. Imagine their marketing people getting heart attacks when some people dare to post pictures of their shiny Apple hardware online and the magic mouse has a wire attached.
