Seed selection is of significant importance for the biased PageRank algorithms such as TrustRank to combat link spamming. Previous work usually uses a small seed set, which has a big problem that the top ranking results have a strong bias towards seeds. In this paper, we analyze the relationship between the result bias and the number of seeds. Furthermore, we experimentally show that an automatically selected large seed set can work better than a carefully selected small seed set. Categories and Subject Descriptors H.3.3 [Information Systems]: Information Search and Retrieval General Terms Algorithms, Experimentation, Measurement Keywords Biased PageRank, Link Spamming, Seed Selection