As I'm typing this, the CBOE quotes and data page lists GOOG and FB options with expirations of September, October, November and December of 2012. But AMZN and GS only get September and October of 2012. Why is this?
The CBOE Rule Book, Section 5.5 explains exactly what programmes are available, how and when they will start listing and expire.
The super-concise summary is: It's a per-underlying decision process, though there's some rules that may provide you with a minimum set of options (e.g. the quarterly programme on highly capitalised stocks trading for more than $75, etc.)
For greater detail, for better or worse, you will have to scan the New Listings service regularly.
Without researching the securities in question I couldn't tell you which cycle each is in, but your answer is that they have different expiration cycles.
The following definition is from the CBOE website;
"Expiration cycle An expiration cycle relates to the dates on which options on a particular underlying security expire. A given option, other than LEAPS®, will be assigned to one of three cycles, the January cycle, the February cycle or the March cycle."