This is a great article!
1. You become upset when something you like is questioned.
Fanboys almost universally interpret criticism as a bad thing, generally responding with hostility. The irony of this is that unbridled enthusiasm benefits no one in the long run. When consumer products are blindly followed without criticism, improvement is frustrated and buyers ultimately get the shaft. It's in everyone's best interest to honestly evaluate what's being sold, be that a system made by Sony, Microsoft, or Nintendo.
2. You are intellectually dishonest.
If you truly believe you are always right and can never be wrong, you -- my friend -- are intellectually dishonest. Common side affects include an unwillingness to hear out opposing arguments, an overlying fear of facts, a rejection of the truth, and opining without requisite context or knowledge (even worse, without thoroughly reading the issues being discussed!).
3. You resort to personal attacks during debate.
Fanboys let their myopic revelry define who there are. Pinning your very existence on the success of a mass market product like the Xbox 360 or PS3 can be a scary thing. Thus, personal insecurity often drives fanboys to spew trite insults and hateful speech when engaging with others in a discussion. The Urban Dictionary aptly describes the occurrence, "[They] put down people who don't like whatever it is they like and will disregard any factors that differ from their point of view." If you have a tough time separating emotion from discussion, you might be a fanboy.
4. The defeat of your enemy is more rewarding than your victory.
Rooting for the success of a "team" is one thing. In fact, millions of Americans do this daily for professional sports teams, favored products, even company stock. But relentlessly celebrating the loss of another in place of your own victory is problematic. I'm not talking about cheering when the Yankees lose; I'm talking about finding pleasure in spamming rival console forums, sabotaging Wikipedia entries, and disrupting the peaceful assembly of others.
5. You bring nothing new to a conversation.
Shipped consoles versus sold? We've all heard that tired argument a thousand times. Does it really matter? If you feel strongly about a subject, make an informed, creative case while backing it up with facts and cross-references. Look to enlighten the argument, not rehash the same points ad nauseum. Better yet, try a different approach if you feel you're not being heard. If "you suck" is the best counter argument you have, you're not even trying.
6. You are anti-fanboy.
Don't get me wrong -- no one likes a troll. But if you've made it your life's work to counter and antagonize fanboys, you're only adding to the problem. Anti-fanboys regularly accuse others of being fanboys in derogatory fashion. It's a vicious cycle. The name gets loosely thrown around yet tells more of the individual using the term than the person it's directed at. Calling someone a fanboy without proper cause is merely evidence of a weak mind trying to get noticed.
I have to admit that sometimes I'm guilty of #6... I'll try to control my urges of agonizing other fanboys...
Proud Member of GAIBoWS (Gamers Against Irrational Bans of Weezy & Squilliam)