ATI wants you to overclock. Really, it's OK
Several weeks ago, ATI sent out a few product advisories claiming that AIB partners were free to overclock any GPU in the the ATI X1000 series. Last year, ATI made a similar statement about the X1800 cards, but this is officially the first time ATI has openly sanctioned overclocking any current generation board.
ATI's memo claims manufacturers who "creatively brand" hardware to reflect overclocked values may risk getting cut off from ASIC allocation -- so we shouldn't have to worry about X1650XT Super-Extreme-Edition cards flooding the market anytime soon. However, like with NVIDIA cards, we may see more batch-by-batch overclocks on specific cards. NVIDIA has an open policy on manufacturer overclocks, claiming that the manufacturers are responsible for RMAs. On the other hand, they are also are allowed to push clocks as far as they want.
ATI will still impose partner specific "Shipping Clocks" on all of its cards. For example, your PowerColor card may have a higher Shipping Clock than a GeCube card from the same ASIC. The end user may still use tools like Catalyst Control Center to overclock to a maximum clock specified by ATI. Of course, using a third party tool like ATITool is not sanctioned by the company yet, but there is nothing that would prevent you (the end user) from using that either -- yet.
Interestingly enough, the documentation claims that ATI partners are not allowed to underclock ASICs -- those attempting to get creative with passive cooling will still have to underclock on their own.
ATI claims thermal damage is strictly not covered by RMA and that blown internal fuses in the GPU will notify RMA teams if the GPU has been stressed too hard.