Another thing is, there are 1000 BTC clones but no Ripple clone. Ripples main asset is the gateways and that can't be replicated.
I only fear that Ripple could destroy itself from within, if R.Labs and/or some of the gateways would decide to impose restrictions on the free (as in "mostly anonymous") trading in the Ripple system, out of fear of regulators, aka the Shapeshift-suicide
I think any concern about Ripple not being decentralized enough does really mean this worst case scenario.