We have had some considerable positive ranking improvements over the last few months going from #12 to #2 for one of our primary key phrases. Over the weekend, we dropped down to #12 and now are sitting at #10. My initial gut is that there is a penalty of some sort in place? I'm concerned because I am now seeing hundreds of invalid links in Webmaster Tools for this page that ranks well. The URLs of these invalid links are all tied to a highly popular dynamic ip service with close to a dozen different unique domains being used.
Has anyone seen anything like this? I'm guessing that it might be a competitor trying to hurt us? Any suggestions?
I have contacted the dns service in question and they have said that the owner was blacklisted last week and the domains were taken down but they could not give me any more details without a subpoena.