I know there is some RAM that is 1.65v marketed for Sandy and Ivy Bridge. I also know for a fact that Intel will ask specifically about what RAM you were running if you have to use the CPU warranty and will deny the warranty for anything over 1.5v.
Technically going over DDR3 1333 for Sandy Bridge and DDR3 1600 for Ivy Bridge will also void the CPU warranty but as long as the RAM is 1.5v I have not seen any problems by just going over the speed. Due to the memory controller being on the CPU high speed memory is basically a waste of money with DDR3 1600 cas 9 being a sweet spot.
If you do plan on overclocking at all Intel has this special overclockers warranty that covers overvolting.http://click.intel.com/tuningplan/
Crap I was trying to find the actual Intel warranty page. I know for a fact about the RAM voltage because it happened to one of the moderators here on Tom's. There was a huge thread about it that was supposed to be made a sticky but never was.