I wasn't aware of the 10% interest on steem dollars, but it would definitely have consequences in terms of real-life economics if it builds up in terms of people having them parked to get interest.
If steem dollar = dollar, then that would make the steem platform something that would attract a lot of external investment to acquire steem dollars appreciating at 10% per year.
So say a fund comes along and buys 10mn steem dollars in order to make them 11mn steem dollars. That's -1mn dollars for the ecosystem in the end of the year. Is this sustainable? I mean banks get your deposits, give you 2% interest and then loan you with 5% - so they have a business model where they have income. Here there's no income except inflation. So perhaps that would create a lot of pressure in steem price as a lot of steem would be needed to support all the steem dollars interest.