From the webpage:
The Explicit Semantic Analysis (ESA) method (Gabrilovich and Markovitch, 2007) is a measure to compute the semantic relatedness (SR) between two arbitrary texts. The Wikipedia-based technique represents terms (or texts) as high-dimensional vectors, each vector entry presenting the TF-IDF weight between the term and one Wikipedia article. The semantic relatedness between two terms (or texts) is expressed by the cosine measure between the corresponding vectors.
I have no objection to machine-based techniques, or human-based ones for that matter, so long as the limitations of both are kept firmly in mind.
Some older resources on Explicit Semantic Analysis.