A variety of applications can benefit from repositories of linguistic and world knowledge. An emerging approach to acquiring such knowledge is to collect it from volunteer contributors. To increase the volume of contributions, some deployed systems for collecting volunteer-contributed knowledge offer recognition or prizes to those who provide the highest volume of contributions. However, rewarding for volume alone can encourage irresponsible contributions by unscrupulous participants. In this paper, we present an approach to collection from volunteers which incents responsible contributions. Rather than asking contributors to simply enter knowledge, our approach is to collect additional answers by asking contributors to guess partially obfuscated seed or previously known answers. To test the approach, we have implemented an online game, 1001 Paraphrases, and deployed it to collect paraphrases for a specific target application. We present preliminary observations and lessons learned on the success of the approach.