Having a SSD that is worth more than the rest of the computer combined, is kind of an interesting proposition, but if you want to do it, I don't see why not.
The only thing is, unless you're running Windows 7, or a very recent (ie: 2.6.34) kernel, you're not going to have TRIM. This means, over time, your SSD will suffer performance degradation much faster than it would, for instance, on a Win7 machine.
As for RAID'ed SSDs, I really don't see the point unless you have a weird requirement to obtain an enormous amount of space, in which case, you can buy SSDs into the 1Tb range today (ie: from outfits like Pliant, etc.).