Saying that people have some personal subjective valuation of the security in BTC is a meaningless statement, it can not be quantified into value per unit of BTC.  Security is best expressed in a degree of confidence, the percentage probability that I will successfully retain ownership in the face of the random theft/loss chance, over a period of time.  I am equally secure regardless of how many BTC I own so why is a larger quantity worth more then a smaller quantity?  Lets suppose my confidence level is 99% per year, how do I turn that number ALONE into a valuation?  I would need to multiply it by a value derived from backing and take into account the risks that are inherent in any backing.  The only thing BTC enthusiasts can point to to back the UNIT of BTC having value is the ability to sell them to the greater fool in the future, aka they are not backed.