I wonder what happened that got this pulled so fast -- if I recall correctly, I found it (and posted it) back in August. So booking.com got "tired" of topcashback in something like two months! Yet, they're offering a similar deal with other referral sites. Weird.
Please let us know your success in getting the cashback credited with the various sites. I'm particularly curious if consecutive nights at the same property will generate additional cashback. I recall the terms and conditions suggest (ambiguously) "no," but I think I always got the credit with topcashback.
I used MrRebates yesterday for the 10 bucks. I've had an account there for years, so I know they're reputable. Not sure if you can still do it, but MrRebates used to have a referral program where you'd sign up and earn 20% on someone else's purchases, while they earned full credit. I referred my wife, and it's worked fine for years. So, in this case, it would amount to a total $12 per night cashback. Not as good as topcashback, but nothing to sneeze at.