For those who have never felt addicted to a video game, the concept of wanting to play a game almost like an addiction might not make much sense. But there are a variety of games like Farmville, MMORPGs, and others that can become addicting once getting into the game and playing them.
The first reason for the addiction is that they are based on a system of constant rewards. It feels good to get a rewards regardless if it's a compliment, pay, or even a virtual item in a video game. The feeling of achievement is still pretty much the same. As you play a game and get constant rewards, it can create a good feeling that people want to get through the day.
Secondly, games like Farmville are played in real time. It's not like traditional video games where the world stops when you do not play. Games that are in real time still have an existing world. There is a desire to come back into the virtual world to keep up with what's going on.
In these simple types of games you do not get stuck. In many linear games when stuck, you either figure it out or get frustrated and walk away. When you do not have a good idea of what to do next, it's easy to shut the game off and do something else because being stuck is stressful. In games like Farmville, you can not get stuck. Since you always know what to do next it is easy to sit down and lose track of time always doing that next thing that you know needs to get done.
Lastly, there always one more thing to do before signing off. When you have a constant list of things that you can do in a game, you want to get that last thing done. This becomes another and another. Before one realizes it, hours can pass before actually stopping the game.
While some of this might seem a bit pickle, the reality is that this type of experience can soak up hours of time and cause problems for those who feel addicted to them.