Feedback is important to the creative process, but not everyone has a personal crowd of individuals they can turn to for high-quality feedback. We introduce and evaluate Critiki, a novel system for gathering design critiques on crowdfunding project pages from paid crowdworkers. Stemming from previous research on crowdfunding project creators and their need for early-stage design feedback, we design and build a working system which fits the need of this population: rapid and inexpensive feedback. To solve issues with critique quality we describe a scaffolding technique designed to assist crowdworkers in writing high-quality critiques. We evaluate Critiki with two field deployments: 1) A randomized controlled experiment with 450 crowdworkers to evaluate the efficacy of the scaffolding technique and 2) A user study with 31 crowdfunding project creators to determine usability and user satisfaction. We contribute to research on Creativity and Cognition by demonstrating a working creativity support system, empirically evaluating the system, and describing how scaffolding approaches can be designed for other crowdsourced tasks.