Seems like just about anything can become an addiction nowadays. With the advent of social networking sites like Facebook and MySpace, people are spending more and more time online. Now, I personally think that these are a good thing, up to a point. They allow us to re-connect with family and friends we haven't seen in years - classmates, long-lost cousins, college friends - but too much time online can be unhealthy.
The games available through Facebook can be really addictive and time-consuming. They can also be a nice way to spend a rainy Saturday. Too much of a good thing can turn bad, and this goes for the Facebook games.
People tend to live on the computer when they are first introduced to Farmville, Cafe World, Zoo World and the other Facebook games, but for most people the "new" wears off after a few weeks, and they turn to other interests. If you find yourself glued to the computer planting new crops after six months, then you are addicted and need to think about limiting your time online.
Yes, it's a lot of fun, but when it interferes with work, school or socializing, it's too much.
Are you addicted? Think about it.