According to a report on one of my colleague’s web sites (http://www.trademarkia.com/opposition/opposition-brand.aspx), Apple and Zynga take the third and fourth position in the list of trademark ‘bullies’.
What does this mean? Simple: they have opposed more trademark applications than other trademark holders.
This is important if you have Apps. Why? Because Apple and Zynga are voracious App filers, and will protect their App Icons from competing Apps. Needless to say, Trademark ‘bullies’ take a stance that everything infringes even if it does not, and the victim has to prove otherwise.
In conclusion, it is of the utmost importance to protect your App Icons as Trademarks before more ‘bulles’ get on the field and shut you out.