What of heroin's merits as a drug? Does it do a great job of expanding people's minds and letting them see mundane experiences in new and interesting ways? Does it bring people together to help one another? Can it help people who have legitimate medical problems by reducing their suffering?
People don't do heroine because of its abstract, broader merits as a drug. They do heroin because it feels good and because doing heroine makes you want to do more heroin. We don't analyze heroin in the hopes of discovering how to make commercial drug products more addictive and deride heroin for being "not a drug."
Farmville is an effective social parasite and advertising mechanism. The game is designed directly to extract money from players. Analyzing it as only a game is pointless, because its manifestation as a game is just the very blunt tip of a sprawling iceberg. Analyze it as a business. Compare it to direct mailing, viral videos, and banner ads.
Farmville is the ultimate sign of the commoditization (not really the traditional sense of the word--the mass marketization is more what I mean) of gaming. The games industry is maturing. "Make games we want to make and hope we get paid for it" has been replaced by "make games that we will get paid to make." The same happened to the music industry--and will happen to any art-based industry as it matures. The business model now drives, not the content. The cascade of free-to-play games and nickle-and-diming DLC are the first steps large steps down this long road. Sequelitis is merely a symptom. We can't go back to the good old days (if they even existed), we must recognize the shape of this beast and confront it directly.
This is another reason why I have stopped playing MMOs.
[EDIT: Made some corrections thanks to an anonymous commenter who apparently deleted his comment...]