What? Ideas absolutely can be property. Hence copyright and patents.

I'm pretty sure if I wrote a book called the "Adventures of Harry Potter," I would get sued immediately.

If what you actually mean is that ideas can't be copyrighted, then yes, you are right.

Content, or simply works, is different: in most jurisdictions, whenever you create anything, you own its copyright whether you like it or not. In Europe, IIRC, there is not even a way of waiving that right.

The point here is that AS crawlers not only use but also reproduce information (sometimes verbatim) they don't own the copyright for and is therefore not theirs to publish. As anyone who went to the university knows, presenting the work of others as yours is the one thing you're not allowed to do.