Lot’s of people have received the unnatural link warning for their sites in Google Webmaster Tools but simply have no clue whatsoever of what links Google is considering to be nasty.
When you don’t know there is a risk that you are deleting links you shouldn’t delete and take unnecessary risks and may lose rankings and traffic for nothing.
Google seems to have acknowledged this issue and there is an
upcoming solution for that at according to Matt Cutts.
There is no exact date set for when this will be implemented or if it will be implemented for sites that already have received the unnatural link penalty or if it will only be something implemented for new messages
but soon there will be an example or two sent together with the message showing what links Google believes are hurting your rankings.