The problem with that Survivor/Russell Hantz situation is that the source was Russell Hantz, and he had to sign a confidentiality and non-disclosure agreement as a condition of being cast or each season.
Anyone serving as a conduit for Russell's information would therefore shared liability for violation of the agreements Russell signed, and that's why Burnett sued.
If the information has come solely from sources who have not signed any confidentiality and non-disclosure agreement, such as bystanders who recognize the identity of a contestant or recognize the tell-tale signs of the production crew of a particular show, that is not a violation of any contract. (Thus, adding two and two to get four isn't a violation where both of the 2's came independently of the cast and crew, or where the observer figures out that the correct information wasn't what they were told, or they just overhear or see information in possession of the cast or crew.)
And when people sign waiver to use their images in a show (i.e., locals) I'll bet that there no non-disclosure or confidentiality agreement in the waiver. There's no consideration for it (i.e., the bystander isn't being paid for use of their image in the event he editors put it in. But an 'extra" used for a task is an employee or contractor of the show, and thus, those arrangements can have nondisclosure-confidentiality agreements.
So as far as lawsuits are concerned there has to be a contractual agreement that includes a confidentiality-nondisclosure agreement. Otherwise, there is no basis for a lawsuit.
The real issue is being sure that a source isn't bound by such agreements; when they are using the information before it's aired or released by CBS then becomes a problem.
That should just about cover the legal part of it.
As to my own attitudes about spoilers -- I've found it doesn't tend to distract my interest. Even if I 'm aware of team placements, that alone doesn't tell you how or why a team was first, last, or in between. Even the Sydney leg of TAR 18, as well spoiled as it was, didn't tell is everything, such as why the Cowboys fell so far behind reaching Biondi Beach. We didn't actually learn the story until the episode aired.