Sorry to say, ethel is right; raid-0 shows well in artificial benchmarks, but this does not translate into any real benefits for you and me as single desktop users . I have used raid-0 with the original raptor, SCSI 15k drives, and their performance is not noticeably different from a single 150gb current raptor. Do the research. Why might this be? If a data record is split up into two parts and put on two drives, then it takes two i/o operations to read it in. The positioning(seek) is independent and the reads might happen concurrently. For big sequential reads, this is good. For short random reads, this is bad. If you are using that second core of your C2D, you might be doing i/o that steals the actuator and negates this nice sequential scenario.
While we are at it, NCQ(non-sequential queueing) sounds nice, but for the single desktop user it can actually hurt. It is designed for a server environment with many concurrent random reads.
None the less, do not fear your data exposure in raid-0 for two reasons:
1) The Mean time to failure of a raptor is supposed to be 1.2 million hours. At 24 hours per day, 365 days per year, that is 136 years. Even with several, you are not going to fail often.
2) If you have data that you don't want to lose; BACK IT UP! Raid-1 and the other variants just reduce the recovery time.