According to this article from the USPTO, Mattel, Inc. is the most active user of the PTO's Trademark Electronic Application System (TEAS). The same article also announced TEAS' one-millionth electonically filed trademark application by Donald Junck for his BAIT CRAFT trademark. Congratulation to both Donald and Mattel.
Digging a bit deeper, Mattel filed 780 application in 2006 (search strategy: 2006????[fd] and (mattel)[on]). Notably, 778 were filed as intent-to-use applications (search strategy: 2006????[fd] and (mattel)[on] and (1b)[ob]).
Technorati Tags: trademark, registration, intent to use, mattel, search, strategy