1. You can do crowdscanning, that's what Project Gutenberg and Distributed Proofreaders were doing for the twenty years before google came along.

2. An individual line from a book is copyright, unless you have a fair use exclusion, which would not be the case in these circumstances.

I agree with #1, but for #2, is there precedent or case law to support your assertion? Google's Book Search is premised on the assumption that "snippet" display is fair use, but the suit against them was grounded in the fact that they copied entire books. Typically snippets are longer than sentences.