You should be as comfortable running the (proposed) attestator on your machine as you are running anti-virus software. In thinking about it relative to anti-virus, I came across an insight:
The Web Environment Integrity proposal isn't much different than requiring that, in order to receive an email, the sender both secures their machine with anti-virus and provides proof to you, the receiver, that the message in question is virus-free. Otherwise, without this proof, you won't accept the message.
Metal detectors and the requirement to pass through one to enter certain, defined spaces are probably the physical analogy that people are most familiar with.
The Web Environment Integrity proposal isn't much different than requiring that, in order to receive an email, the sender both secures their machine with anti-virus and provides proof to you, the receiver, that the message in question is virus-free. Otherwise, without this proof, you won't accept the message.
Metal detectors and the requirement to pass through one to enter certain, defined spaces are probably the physical analogy that people are most familiar with.