There is an article about this on the St. Buryan community site [link removed, article no longer there]. I had spotted similar strange entries in my logs so now I know what it is all about. Well, actually I don’t but at least it gives me a hook to find out!
I have come to the conclusion that this is all a bit of a storm in a teacup. An interesting diversion but nothing much to worry about. Perhaps they scan a bit too often but, in amongst the rest of the high volume of search engine spider traffic, it is insignificant.