It appears that, whilst Sharpie® enjoys full trademark protection, Dumpster® is now regarded as a 'genericized trademark' - http://en.wikipedia.org/wiki/DumpsterJoeN:
Sharpie® is a trademark. By definition, all Sharpie®s are name-brand.http://www.sharpie.com/enMY/SharpieInfo/Pages/Trademark.aspx
Gotta go now, taking trash out to the Dumpster®...
(I'm not sure why, but I'm still a little bit startled by the fact that there exists such a comprehensive wiki entry on Dumpsters.)