Just by using the forums, you're already part of giffgaff's "property".
Much like if you use Google's services, you're agreeing to let the company acquire data about your usage.
Klout, whether you like it or not, is being used.
For anyone who truly wants nothing to do with it, the only guaranteed way to avoid it is to stop using these forums.
We can complain all we want, but it's a "feature" that giffgaff want to use.
So c'mon then, how many people are going to stop using these forums and give up on payback?
No. We'll moan about it. We'll ask for our voices to be heard, but giffgaff isn't the same giffgaff as it was a few years ago.
But we'll still come here to chat and discuss things.
We'll still earn payback.
After six months we'll have forgotten about Klout sipping our personal data because it'll be time for another payback pay out 😉