Petch is correct(ish). Adding additional spindle drives to RAID0 has three effects:
1) Increases throughput, this does not scale linearly. Three drives capable of 100MB/sec read and write will not give 300MB/sec read and write. A better controller will help here.
2) Increases access times, you now have another disk head that needs to get into position to get your data. If these disks were SSD's you can ignore this point as their seek times are close to zero anyway, 30 x almost nothing is still almost nothing.
3) Increases failure rate, you now have an additional device that can fail in a system where a single failure completely bones you.
What this means for desktop performance? Two spindle drives IMHO is the sweet spot for desktop RAID0 performance, you have the throughput, but you are starting to increase seek times and random IO, this will decrease the snappy performance of your system.
You may want to look at your controller, if you are using the onboard RAID controller there are throughput limitations, I am rocking a ICH10R and I am limited to ~600MB/s, adding an additional drive to my RAID0 would be pointless. Those Raptors are pretty fast and its likely that you are going to be hitting a point of diminishing returns pretty quick.
Who wears pants to work anyways?