Pinterest has updated its guidelines for contests to avoid spam. The new rules prohibit contests that suggest Pinterest sponsors or endorses them, require users to pin from a selection or pin the contest rules, run sweepstakes where pins/likes are entries, encourage spammy behavior like asking for comments, ask users to vote with pins/likes, or require a minimum number of pins. The goal is to prevent contests that motivate irrelevant or spammy pins rather than pins users are truly interested in.