magic mouse keeps losing connection

Try changing the batteries.

Mine did this all the time. Contacted Apple support under extended warranty - they sent me a new one. Exactly the same problem.

I had the same problem recently after a few years of faultless performance. I read somewhere to clean the contacts inside the battery compartment. I polished them with a dry cloth and it solved my problem.

Over the past 24 hours my MM has been losing connection with my iMac. After reading some of the comments here I took the battery cover off and found a couple of cat hairs near the contacts. Next I cleaned and polished all contacts including the batteries. I'm pleased to announce my problem appears to be solved! In short, it's probably a good idea to start with the simplest steps to solve a problem.

I have bought two replacement magic mouse's (mice?) they both lose connection constantly thought it was battery connection and tried those remedies, found out on both the on switch has failed and with just a little vibration turns it off after it gets a few months old, contacts are very weak is my guess. After giving apple money for two mice that failed within a year or so have gone to trackpad. Mice are cheaply made and not reliable. Guess apple isnt up to par with microsoft on this. Feel taken on the two I purchased, the trackpad however is working fine.

further tear down of my now three faild mice shows the battery bar on positive side breaks free of the heat stakes and allows intermittant battery connection, all three exhibit this breakage, poor design

On my Mac it said I had 47% battery life left. I went to my local battery store and they said my batteries were dead. I bought new batteries and problem is solved.