What LinkedIn is doing seems more like a pool threatening to sue people that look at the facility itself, from outside of their property. It's not clear whether viewing a public website is more (reasonably) similar to entering someone's property versus looking at their property from outside of it. To me, it seems much more like looking at it from outside. But, fortunately for LinkedIn, they can prevent people from viewing their site! (They just have to figure out for whom they want to do so.)