Fanboi pre-dates both Avril Lavigne's "Sk8er Boi" song (2002) and Apple's iDevices (iMac, 1998), however usage increased dramatically since the 2007 release of the iPhone, and it is now often used a a put-down when talking about zealous Apple fans.
The excellent Technologizer post says "fanboy" originates from the comic collector world, and the earliest references to "fanboi" I can find in Usenet are also from comics groups.
In a 9th October 1996 post to rec.arts.comics.misc, The Comics Journal wrote:
With our renewed dedication to running more reviews, we'll surely end up
dealing more with the mainstream in terms of general reviews. We're also
dedicating a new nearly-every-issue column to the mainstream called "The
Fanboi Politik" by Ray Mescallado. I'm sure many opinions and critical
views will be heard on mainstream works in coming months.
Two days later, PatDOneill replies, showing from the start the term has a somewhat negative flavour:
Oh yeah--that title surely indicates what an even-handed approach it's
going to take.
Migawd--you can't even title a column about mainstream comics (that you're
touting as being written from an appreciative standpoint) without
insulting the people who are fans of such work.
How about if WIZARD retitles its column about alternative and small-press
titles as "The Nihilist, Black-Clad Claptrap"? BTW--ours runs EVERY issue.
Ray Mescallado's signature in a 22nd November 1996 rec.arts.comics.dc.lsh post was:
* Ray Mescallado * "The politics of failure have
* fan...@avalon.net * failed. We need to make it
* http://www.avalon.net/~fanboi/ * work again." - THE SIMPSONS
The post was asking the Legion of Super-Heroes "fandom" their opinions of the comic for the Comics and Animation Newswire. He wrote a lot about "fanbois".
The earliest Urban Dictionary definitions aren't until 2003, but both clearly have negative meanings:
Someone who is hopelessly devoted to something and
will like anything associated with their particular thing.
That damn fanboi only likes that game cause Capcom made it.
The only reason he bought that car is cause he is a Japanese fanboi.
Source: Jevin, Jun 19, 2003
Alternate of fanboy.
You must be either retarded or a fanboi.
Source: loser, Apr 7, 2003
More recently, both fanboy and fanboi are used to describe zealous fans of technology and products, in addition to comics, games and films. The use of fanboi is especially used to describe ardent fans of Apple products, and in particular appears to have increased dramatically around the 9th January 2007 announcement and 29th June 2007 release of the iPhone.
The Register is an IT news site particularly fond of iconoclastic slang. A quick tally of their 116 articles including the word fanboi show 111 are in the context of Apple/iPhone/iPad/iMac/Mac/MacBook. (The others are Java (x2), Rackspace, AWS, and e-voting.) The earliest was published in an article titled "iPhones, iPhones and more iPhones" on 13th July 2007, and is a round up of comments following the recent US release:
I _heart_ Apple
..........Insert sycophantic drivel here..........
Google's Insights for Search backs this trend up. The main peak begins in November 2006, soon before the iPhone's official January 2007 announcement, as hype around Apple's rumoured iPod-mobile phone was "reaching fever-pitch".