The review campaign seems to be an exclusive campaign and it is not being published publicly. Someone reported in the previous page that he received an email from trustdice offering a reward if the user want to make a review. That's might be the reason why you cant find a review campaign thread as it is availble for their users only or maybe they do it randomly.
To get more traffics and more participants, they can publicly announce their review campaign in the forum.
They don't have to worry that they have to increase their budget to pay for participants. It depends on their terms for the review campaign like only accepted reviews will be paid or only top 20 or 50 best reviews can be paid.
Best reviews should be reviews that can help TrustDice team to improve their service, and should not be reviews only say good words about TrustDice.