Anyway, I was wondering if anyone had heard of a successful case where a domain name was taken away from a squatter based on common law trademark?
I have a client whose company and company name is 100 years old, but has never been registered federally. It does fall under common law trademark, I believe. Anyhoo, the plural of their name (which actually is probably what most people type) was registered awhile back by a rather notorious squatter and I have done all the offers to buy and what not to no avail. They won't even give me a huge price to pay for the domain.
Is there a case where a common law trademark succeded in getting a domain away from the squatter?
Might be time for the old fashioned lawyer letter. At the very least it may cause the domain holder to remove any misleading or mis-directing links. Kill the profit (arising from any confusion or exploitation) and you may kill the domain holder's interest in keeping the domain.
If your client's business name is a very generalized or generic name it might make things a bit more problematic.
Prior usage is everything in trademark law, whether the name has been formally registered or not. 100 years of use in interstate commerce would likely impart a lot of strength. On the other hand, if the mark is merely descriptive or generic, it could be weak. If the name is entirely fanciful, and/or unique enough - and especially if the average user could derive little clue about what the company actually does or sells from its name alone (eg: Amazon, eBay, Yahoo, Google, Kodak, Exxon) it's considered a much stronger mark.
There's also a fundamental ancient legal principle called Laches. In a nutshell, if your client has rights of ownership in this trademark and does nothing to enforce its rights against parasites and pests, those rights can lapse away, evaporate. Especially if it can be proven that you were aware of those junior users, and it can, because apparently you two have already exchanged communications about the matter. Trademark holders are legally bound to pursue each and every illegitimate user of their marks. Let the stalemate go on for a year or two or three, and you might find yourself at a big disadvantage, and holding a considerably weakened mark.
So yeah - you ought to talk to an attorney, and soon.