Firstly, thanks for making some sense of the ever-growing world of material references. Just today I was introduced to three new libraries, none of which appear in your list. Now with the naive questions: with all the free libraries, why even consider the ones that aren't free? And how much time would you expect it takes for the number of libraries 1) to stop increasing and 2) to reduce to 3 or 4 reliable and user-friendly ones? I feel it's unrealistic to expect professionals to search 12 libraries, and it would be a shame for the library with the better marketing power to take over the better content libraries. Can we count on LEEDuser and the USGBC to help guide professionals towards the most pertinent information, and to help narrow down the field? Help us steer clear from "opportunistic" libraries? It's unfortunate that the interest and curiosity I initially felt about the more in-depth approach to material considerations is now drowning in information overload.