Imagine a sole proprietor who chooses a unique word for a business name - e.g. horsense - then buys a matching domain name (horsense.com). The company name, Horsense, appears on the website's home page and on books written and published by the owner/webmaster.
If I understand correctly, Horsense is essentially a trademark by virtue of its being adopted and used and is therefore classified as an unregistered trademark by default.
Now imagine someone who has a Facebook page at Facebook.horsense or a Twitter handle @horsense
If I officially register horsense, can I then legally compel these users to abandon their horsense "identities," or are they allowed to retain them? I've read that merely contacting Facebook or another social network will sometimes get the job done. I just wondered how much leverage I have if Facebook and the owner of Facebook.horsense.com refused to cooperate.