Having recently upgraded from a Motorola v600 to the ever so slightly different v635 I was disappointed to see they hadn't fixed the annoying side buttons. Basically when the phone is in your pocket it's easy to change your ring style without knowing as the side buttons stick out a little too far. Also every time you accidentally hit those buttons it makes an annoying sound - assuming of course it hasn't already knocked itself on to silent - grr!
I've now found a solution, thanks to this thread on HowardForums. The solution (to lock access to the ring tone setting) works very well. Now in order for me to change the ring setting I just hit the side button (which now doesn't beep or do anything) and then flip the phone open. It prompts me for the passcode (1234 is the default on mine) and it then allows me to change the setting - it's an extra step but a quick one and it's great to no longer beep when I walk!
Update (Jan 21): Damn, turns out that while that solution (above) stops you accidentally changing your ring tone, it doesn't stop that annoying tone when you hit the button. If anyone finds a solution to that then let me know!