ShareAlmost daily we block new users from several spam domains who are trying to post comments (automated) to embed links to what I assume are their clients web sites. The comments generally go along the lines of "Thank you for such wonderful information ..." or something equally inane, and embedded within is a link to a cut-rate mortgage company or report writing service etc.
Let me make myself perfectly clear. We delete these comments as soon as we find them, and block the users who have posted them on EVERY SITE WE HOST!