This document discusses crowdsourcing approaches for solving problems in semantic web technology. It defines crowdsourcing and the semantic web. There are many challenges to using crowdsourcing effectively for semantic web tasks, such as determining the appropriate form of crowdsourcing for different tasks, how to combine crowd and machine intelligence, and how to encourage participation. The document reviews different forms of crowdsourcing projects and discusses factors to consider in task design, quality assurance, and incentives. It also summarizes some research on improving paid microtasks and hybrid crowd-machine approaches. Several open questions are raised about the fundamental challenges of using crowdsourcing at the necessary scale, scope and sustainability for knowledge-intensive semantic web problems.