A couple of years ago, a company called Axiotron announced an aftermarket modification for the MacBook that converted the Apple laptop into a tablet. The modification remains for sale at $699 and takes a stock MacBook, removes the keyboard and screen, and adds a Wacom pen-based screen to give the device a tablet form factor.
Axiotron originally began marketing the devices as a "TabletMac" as referenced in this 2007 press release and filed a trademark for the term. Sometime in the past year, however, the trademark was transferred from Axiotron to Apple, and Apple is now listed as the owner of the trademark.
It's funny that Apple would dispute this with Axiotron (which is a joint venture with Other World Computing) - On Apple's Copyright & Trademark Guidelines page - they have this:
c. “Mac” is used in combination with another non-generic word.
Acceptable: MacVenus MacCharlie
Not acceptable: MacCharleston MacSales
The website for Other World Computing is WWW.MACSALES.COM