Perhaps summarizing the issues that @webcoop has raised, I think it is important to give more weightings to objective measures that are not influenced by individual preferences or subjectivity (because it is impossible to create a 'fair' algorithm based on it). As someone who has worked in user experience design, half of the challenge with the job is to try and work out something that is intangible (what is the thing that someone 'experiences') and translate that into something tangible (i.e. a button that they want to push). More on that in my next post...