I started a series of articles, which got some criticism on LW in the past, dealing with this issue (among others) and this kind of ontology. In short, if an ontology like this applies, it does not mean that all computations are equal: There would be issues of measure associated with the number (I'm simplifying here) of interpretations that can find any particular computation. I expect to be posting Part 4 of this series, which has been delayed for a long time and which will answer many objections, in a while, but the previous articles are as follows:

Minds, Substrate, Measure and Value, Part 1: Substrate Dependence. http://www.paul-almond.com/Substrate1.pdf.

Minds, Substrate, Measure and Value, Part 2: Extra Information About Substrate Dependence. http://www.paul-almond.com/Substrate2.pdf.

Minds, Substrate, Measure and Value, Part 3: The Problem of Arbitrariness of Interpretation. http://www.paul-almond.com/Substrate3.pdf.

This won't resolve everything, but should show that the kind of ontology you are talking about is not a "random free for all".