The site aims to keep high standards and attract experienced and knowledgeable practitioners of chemistry. The point is to share knowledge, not "doing someone else's work", but that is just what happens when you provide an answer, you are doing the hard work by helping someone figure something out which would otherwise take them much longer to do.
Addressing requests from fellow researchers for information on a relevant chemical topic is similar. Finding a reference is often one of the most critical steps to making progress with a research question. But helping someone that way provides a shortcut and risks being labeled as "doing their work". Also, it does not clarify a topic but provides a place to look for the answer, and may be opinion-based (although clearly any helpful reference is helpful, so this argument seems nonsensensical to me).
This post asking for a book on a narrowly-defined chemistry topic was closed as opinion-based. While the opinion-based nature of book and reference-requests in general has been mentioned before (books, reference-requests in general), this doesn't strike me as entirely justifying the closure.
[note I added the reference-request tag to that post after it had been closed]
Clearly there is a line there, fine or not, and opinions are bound to vary. It'd be nice to resample opinions and if possible specify more accurately where the line does and should lie.
More elaboration or comment on the usefulness of these tags and on guidelines to determine when such questions should be closed would be useful. Ideally backed by examples of posts which requested such information deserving to remain open or deserving to be closed.