I have been wondering something for a while now. We have a manual penalty from Google on unnatural linking. When I check out Links to your site in Webmaster Tools we have 11,387 links from Meetup.com. Is this harming us? After clicking through some of the links randomly I have discovered it is from one of our dealers that sells our products. He is sponsoring different groups and so the ad appears, the problem is he is linking back to our site and not his own. The anchor text is all the same it never changes. 
Thousands of backlinks from Meetup.com
seo;links;backlinks