Not for recommenders, but we have worked on using LSH for spotting breaking news in Twitter.
Our experience is that it works well when the points are actually close together, but you do need to tweak it (eg work-out the number of hash functions to use and the number of tables). There are also technical problems dealing with spurious matches --new points that look really different to previous ones might match in non-intuitive ways Miles -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336.
