It's value is based on its scarcity and its scarcity is based on a degenerative "mining" algorithm that was written by Satoshi originally. People smarter than me have looked at the algo and determined that it is legit, but even a tiny weakness could be exploited to effectively blow the scarcity-value all to hell and any investment in BTC would be lost.
Even being in the biz (or maybe BECAUSE I am in the biz), I am still skeptical of BTC as anything other than a very short term anonymous storage of value. I am in and immediately out as necessary.