Re: "May have been (at least in US law) legal"
It's complicated, which is the whole basis of this case, by the content being publicly accessible.
Because Linked In has "private" content, it also means that what it publishes outside of this is "public" content. As in freely available to all. The presentation of this content is subject to Linked In's copyright, however the content itself is provided and therefore (co)owned by the data subject, who has "chosen" to make this information about themselves freely available to the public. Linked In benefits from this content being freely/publicly available as it drives searches to the Linked In service through search engines. Linked In cannot have it both ways unless they want to specifically go down the route of licensing search engines to access content and to also have the data subjects (users) of the service agreee to this.
It's an interesting situation that largely benefits lawyers, who without this kind of thing would doubtless struggle to maintain their (frugal) lifestyles.