Another variety is the sole posting of a URL or link that leads to material that might be used as a discussion primer, but with no added opinion of the poster. It differs from plain spam since forum spam often is posted by spambots, while hit-and-run posting on the other hand is done by a real person. Also, while spam mostly consists of advertising, hit-and-run posts usually have at least some bearing on the topic at hand. However, since the poster doesn't stay around to defend the posted material, or even discuss it, it is considered disrespectful, especially by forum regulars who tend to be angered by the fact that the hit-and-run doesn't become obvious until some or several replies already have been made.