The word defining folks over at Merriam-Webster Inc. have added "Fanboy," along with 100 other words, to the newest edition of its Collegiate Dictionary*. Fanboy is actually one of the "oldest" of the "new" words, with its origins dating back to 1919. The wordsmiths define fanboy as a "boy who is an enthusiastic devotee, such as of comics or movies." Fanboys should feel free to write with self-righteous fury to MW and let them know it can also apply to video games ... tell them you'll never read their dictionary again if they don't correct this grievous oversight (also make an online petition).
This isn't the first time in recent memory some bit of gaming culture seeped its way into the good word book at Merriam-Webster; "w00t" became the company's word of the year in 2007. So, w00t to all the fanboys out there, the dictionary acknowledges your existence.
*OSX users will find the Dictionary widget, which uses The Oxford American Dictionary, already defines "fanboy." Merriam-Webster is a different company.