Did you ever write an e-mail? Well, you probably used the @ sign then.
On the site, http://en.wikipedia.org/wiki/At_sign I just found the strange sentence
Since 23 October 2012, the At-sign is registered as a trade Mark by the German Patent and Trade Mark Office – DPMA (registration number 302012038338) for @T.E.L.L. Trading house for exclusive luxury labels GmbH, 69469 Weinheim, DE. From now on it’s illegal for other commercial interests to use the At-sign.
which does seem to be a strange kind of Wikipedia humour, doesn’t it?
Of course, a German patent only applies to a class of goods. In this case, the patent was not applied for the use in IT, so it is _not_ illegal for commercial companies to use the At-sign. Perhaps I don’t understand Wikipedia humour.