I have done something similar to help with building negatives for an Adwords campaign for Centre Parcs in the UK I used the Levenshtein edit distance to genera

I have done something similar to help with building negatives for an Adwords campaign for Centre Parcs in the UK I used the Levenshtein edit distance to generate a list of potentials for human review - I extended MySQL to have a Levenshtein distance function for speed.