Memory frequency should Match FSB?

The answer to your first question is that it doesn't really matter much. You could slow it down, to run 1:1 with the CPU, and lower the timings and there should be a very slight, barely noticeable improvement in speed.

The answer to you second question is no. It doesn't matter if it's a single, dual, quad or whatever core the FSB is the FSB so 1066 is still 266.5 quad pumped and runs 1:1 with 533.

For Intel processors, the speed the memory runs at makes little performance difference. It all is tied back to the FSB of your CPU. No matter what you use or how you set the multipliers, it all goes back to and is based off of dividers/multipliers running the same speed as the CPU buss speed.
Lower latencies or timings will show a better improvement in speed, but it too is a barely noticable improvement.

How many cores a CPU has is not part of the equation. All CPU's no matter how many cores they have, all work off of the FSB the same way.
2 cores has no bearing on buss speeds/multipliers or dividers vs a single core, or quad core.

Manufacturers are coming out with higher speeds
1. For overclockers who still want to run things 1:1
2. To make more money.

All integrated circuits are not created equal. With each batch made there are some that are formed perfectly and some that are not. The more perfectly formed, and higher performing, chips are sold at higher speeds which is why manufacturers started coming out with voltages over the JEDEC DDR2 standard of 1.8v. These chips are capable of higher performance than some others and rather than just release them all as DDR2 800 or whatever they created new categories and sold them at higher prices. Manufacturers also realized that the SPD (Serial Presence Detect) chips on the RAM that hold the information on timings and voltages had more room so they started putting multiple settings on them. You might buy DDR2 800 but it will have settings for 533, 667 and 800, all with different timings and some with different voltages.



This is an example from my old RAM. As you can see there are several different settings, some JEDEC and some EPP (Enhanced Performance Profiles). It was sold as DDR2 800 4-4-3-10 2.1v