You raise some good points here. I’m still undecided on the issue, though I am leaning towards the camp that wants 1:1 parity with the USD. Here’s why.
SBD are Steem Backed Dollars. For every SBD there must be an equivalent amount of Steem which has been powered up into Steem Power. At the moment the market cap of SBD is much lower than the market cap of Steem which has been powered up and it should remain so.
My concern is that with a floating SBD the price could be bid up by a powerful adversary until the market cap of SBD is greater than that of SP. If that happened we would essentially have a fractional reserve (fiat) currency. Look at what is happening in the US and EU to see how that plays out in the long term.
Another disadvantage I see in a floating SBD is that users of the platform could become disincentivised to hold either Steem or SP, if they saw that potential gains from holding SBD outstripped the benefits of powering up their Steem. If Steemians would rather hold SBD, than Steem or SP I imagine we would see a continual erosion of the value of the reward pool.
There are also disincentives to businesses who would like to launch a platform using SMTs, but I don’t think those points are as valid for typical Steemians as the points I have just outlined.
As I said I am undecided on the issue. I’m very interested to see how this plays out.