1. For the things that RAID 0 helps with, i.e. STR heavy tasks, then yes, 4 drives are better than two (though often limited by the bandwidth to the SATA controller. As seen above, this STR advantage can easily be matched or exceeded by using a drive with better firmware or a bigger cache when it comes to real world applications.
Some benchmarks give too much importance to STR in the overall scheme of performance. STR benchmarks are the obvious example, giving no consideration to cache, access time or firmware optimisations. That's why SR benchmarks drives using recorded (and thus repeatable) traces of real applications.
As you can see from Eugene's results, if you increase STR while keeping everything else constant, you (usually) get an improvement. By using a single drive with lower STR, similar access times but with major improvements in firmware and cache, the improvement by increasing STR alone is surpassed. That should give you some perspective on the relative importance of STR - it helps, but not that much.
2. The maximum STR of an individual Raptor 150 GB is under 100 MB/s. Since each SATA drive has its own dedicated link to the controller, and that link has a bandwidth of 150 MB/s, the link to the drive will never be a bottleneck no matter how many drives you have.
(As long as you're not using port multipliers to run several drives off one connection to the controller. But you'd know if you were.)
With SATA, it's the bandwidth to the SATA controller that will limit STR from a RAID 0 array - anything not integrated into the chipset itself will be limited to the bandwidth of the PCI bus, usually about 120-130 MB/s.
You were probably thinking of PATA, where two drives might share the same cable (channel), so if you didn't have enough PATA channels free to give each drive its own cable (channel), then two drives had to share the bandwidth of one channel (up to 133 MB/s for ATA133).
So, basically, I stand with Eugene on this one. But I'm glad you challenged him - it's important to question any authority if you suspect that it is misleading you. I hope we've reinforced your trust in SR's benchmarks and opinions, but even if not, thanks for giving us the opportunity to try.*
* I should point out that I don't represent Eugene or SR at all. That last sentence was a bit ambiguous, and I don't want to give the wrong impression.
It wasn't me who challenged Eugene. Some other guy on here who was comparing his review to one in GamePC.
My comments were almost off topic to be honest and was a discussion on benchmarking with JLN.