Record DDR3 Memory Overclock on ASRock Micro-ATX Mobo
ASRock has managed to reach an effective DDR3 memory speed of 4285.6 MHz on a Micro-ATX motherboard.
A team of overclockers consisting of Nick Shih, John Lam, and Splave has managed to set a world record for overclocking DDR3 memory. Nick Shih is ASRock's own overclocker. The motherboard that the team has used is the ASRock Z87M OC Formula and, clearly, it is living up to its name. This motherboard is a Micro-ATX motherboard that is targeted at overclockers and gamers.
The overclock that the team managed to achieve is, behold, a staggering 2142.8 MHz (effectively 4285.6 MHz). This feat was accomplished at the overclocking show at Computex. The memory module that was used was a Team Group Xtreem LV-2666 module, 4 GB in size. Timings were set at 14-31-31-50.

1) Knowing that it's possible to do with a specific configuration. Think of it more along the lines of Proof of Concept. Proof of Concept doesn't have to have an immediate practical use.
2) It's about doing it for the sake of doing it.
It's the reason why we drive cars easily capable of exceeding 100mph/160kph, yet very few of us ever go there on a daily basis.
That depends a lot on whether your software is more bandwidth-bound or latency-bound.
Since this memory is running at over 3X your memory's clock speed, the latencies are equivalent to 5-10-10-16 at 1333MT/s which is not that bad. The much higher bandwidth allows filling cache lines much faster and would likely make up for most of the loss on timings.
In general, the only type of code where lower latency systematically wins over bandwidth is very branchy and unpredictable code like compilers. For most mainstream software though, CAS latency and speed grades can be traded for each other with little to no net effect on performance.
Since I have yet to see a DDR3 kit above 3000MHz, do tell where you found these 4800MHz kits.