AddAll, which aggregates multiple book sites, has a box that allows you to eliminate POD results from your searches. If you're looking for an actual first edition of a novel by, say, Amelia Bristow, checking the box should eliminate the fifty gazillion different OCR editions of the novel. Right?
Well, no: the search pulls up fifty gazillion different OCR editions of the novel, because sellers have presumably wised up and eliminated anything resembling "POD" from the metadata. Specifying "first edition" actually eliminates a number of relevant results. Bizarrely, the most logical fix for this problem--allowing users to search by date or date range--isn't an option. (It's possible to insert a date in the keyword slot, but this frequently returns unreliable results, especially if a book went through multiple editions.)