Line-in never automatically updated Spotify data. Spotify matched their data retrieval to user feedback from line-in to check how well their system works; to see how accurate their meta-data is. Spotify has over 96 million premium subscribers, yet the line-in community was only a few thousand? The program in itself was obviously too small-scale. Think about it, if this was the only data they are getting, data from a few thousand "active" users who explicitly give feedback, regardless of how much incorrect meta-data exists, the percentage of incorrect songs vs how many songs their are in the system is so small. Meaning, this was helpful to see how much data was incorrect, but that it was not necessarily a project worth pursing. Unfortunately, perfect data is a goal which can seldom be reached, and many may have conflicting views on for example the definition of genres or what specifically an explicit song entails. Whatever user feedback Spotify was given had to also be checked, most likely manually, and they may not have had the staffing to do so if it was not beneficial when looking at the bigger picture (just speculating here). The truth of the matter is that the bigger a system is, the more difficult it is to maintain. Generally speaking, as long as the majority of things run smoothly and the majority of people are happy, then a company is happy. I think it is very unfortunate that line-in was discontinued, but that is just the way the cookie crumbles.