Correct. It needs to be an 'exchange' vehicle, not an investment vehicle. I'm not sure what to attach it too, but the value of a single bitcoin needs to be tied to something else, and it's worth the exact same value when you put it in as it is when you take it out.
For example...if, lets say, 1 bitcoin is worth $100 (USD). You put in $100 USD and you get 1 Bitcoin. Many years later, you 'cash out' and for your 1 Bitcoin you get $100 (USD). (Depending on inflation that $100 might not be 'worth' as much as it was before...but it's still $100.)
The trouble was because they wanted it to be it's own currency...not tied to anything at all... with the idea of 'exchange rates' and official stuff like that. Instead, it should have been more like the coins and cash of a currency. It represents an amount of a currency and it's used to enable transactions, but it doesn't have any intrinsic worth. (Or rather, its intrinsic worth is unrelated to its face value.)