Depends on the motherboard. Had an HP laptop that was running at an FSB of 1066..........but the RAM ran at 667. Why? Because, explained buried deep inside their owner's manual, was the reason....the memory was clocked higher to accommodate the speed for optimal operation of the onboard video graphics. The manual also said the video would work quite well with the RAM at 533, but optimal RAM speed was 667, and that's what they put in and what it ran at.
So, a lot depends upon what the mb is looking for and why.
And, no, it won't mess anything up....unless your RAM is incapable of running at that speed.