Whether we have fractional reserve and what that fraction is depends the value of NuShares + reserves (such as USD, BTC and PPC) / NuBits in circulation. For example, right now NuShares are worth about 3,000,000 NBT, reserves are approximately 600,000 NBT (total of BTC and PPC held by KTm, Julie Miller and myself), and I believe outstanding NBT is around 500,000. 3,600,000 / 500,000 = 7.2. Assuming these numbers are accurate (they are not) we have 7.2 times as many assets as liabilities. Only if this ratio drops below 1 is there a fractional reserve. Fractional reserve doesn't imply insolvency, but it does imply a vulnerability to it in the case that too many NuBits are sold at once.
The above analysis presumes the existence of currency burning. I also agree with Benjamin that non-NuShare reserves (such as BTC held by custodians) are not of the same quality as NuShares, because it cannot be ensured they will be used to support the peg. Therefore, given the numbers I presented above, there is reasonable debate about whether the ratio of reserves to liabilities is 6 or 7.2, or somewhere in between.
Reserves are useful for providing immediate liquidity. It is worth noting that I have worked hard to encourage liquidity provider custodians to provide their own funds, which in no sense would be considered reserves, which if consistently done would put us in the position of providing liquidity without the use of reserves.
We ought to be able to present the kind of numbers I presented above. This will take the coordination of any custodian who still has possession of NuBits received via custodial grant as well as info about the remaining proceeds of undistributed NuShare sales. Because I do not have current information from other custodians, the numbers I mentioned are only estimates used to explain the significance of this type of information.