There are also legit but over zealous listings. There are apartment complexes that re-post the listings every single day. So, checking if any new apartments appear is always manually filtering over 40% the apartments you've already looked at but which were reposted.
This drives me crazy. I have saved searches for various power tools within a few hundred mile radius. Most of what I see are duplicate posts from people cross-posting in adjacent regions, the same items re-posted weekly (or more frequently), and irrelevant listings that show up due to keyword spamming. I wish there was a way for me to say "I've seen this ad, don't send it to me again unless the price drops". Have been thinking about building some kind of filtering software to eliminate re-posts -- anyone know of a project that does this?