Here's another article about the memory voltage controversy with the upcoming Intel Core i7 processors. Most people are under NDA and aren't willing to say much about it but the guys from AnandTech talk a bit more freely and say the answer isn't simple. They say motherboard makers have destroyed quite a few Core i7 chips by running at high voltages, but in most cases they were testing the boards with memory voltages at 2V or higher.
AnandTech believes voltages above 2V will kill your Core i7 processor in weeks, or even days, but voltages of 1.7V to around 1.8V should be relatively safe, with the right motherboard, cooling, and BIOS settings. However, if you don't have any DDR3 memory or don't mind buying new memory you'll be able to get plenty of triple channel DDR3 kits that run at voltages below 1.65V.
Personally, with the right board, cooling, and BIOS settings, 1.7V~1.8V should be fine (no promises yet) and will allow the upcoming low-voltage, high clock speed DDR3 DIMMS to reach the 1866~2200MHz level. This should satisfy most performance enthusiasts, but probably not the extreme clockers who will try for more. For the rest of us, this platform offers simply amazing bandwidth and latency numbers with tri-channel DDR3 1066 or DDR3 1333. In fact, we think tri-channel DDR3-1333 at 5-5-5-12 timings or DDR3-1500~DDR3-1600 6-6-5-15 settings (1.65V) will provide optimal memory bandwidth, write speeds, and latencies for 95% of the users at this point. So, unlike the P45/X38/X48 platforms, having low-speed rated DDR3 is not going to be a hindrance to extracting fantastic performance from a i7/X58 setup.