WithoutWeakness :
If you have an older power supply that isn't validated but are determined to run Haswell without buying a new PSU you can just turn off the C6/C7 power states in the BIOS to prevent Haswell from dropping power consumption too low and the machine will run just fine (albeit with slightly higher power consumption).
In most systems, the GPU, HDD and other loads usually provide more than enough load on 12V to meet the PSU's minimum loading requirement.
In many cheap PSUs, that minimum load is built directly into the PSU in the form of 2-5W resistors across rails and ground - horrible for efficiency but gets the job done.
I'm sure someone will eventually publish an article about Haswell's PSU compatibility. I would not be surprised if the majority of remotely good non-certified PSUs ended up working fine. I would also not be surprised if they found at least one certified unit that actually fails.