How to create a successful social game?

Recently, I just got involved with a project on creating a social game - a game for social network sites like FaceBook and MySpace. The first important question that comes to my mind is - how to create a successful social game?

There were some articles I read and some observations another team member made. I've summarized them in a check list. The idea is - our game must satisfy all the following items.

To start off...

This list is from a panel discussion with HitForge, First Round Capital, Accel Partners, and Hummer Winblad. It could be seen here on Omnisio.

1. Is it simple?
2. Is it social?
3. Is it viral?
4. Is it universal?
5. Does it gather user data?

Is the game scalable to mobile platforms?

And will the mobile experience deliver the same amount of value and fun as the SNS counterpart? (In other words, the mobile experience cannot be just a gimmick.) I derived this item from an article from TechCrunch regarding PlayFish.

Does it have a business model? Does it have a way to make money?

Here are a list of the popular models I came across.

1. Freemium model - (source: TechCrunch - Free to use. Pay to play)
2. Selling the mobile version of the app (i.e. iPhone app)
3. Advertising
4. sale of contents (i.e. virtual goods, more stages)

And a list of items from another colleague

1. Does the game have interaction with other friends?
   This means it cannot be a standalone game. Examples involve teaming up with friends and trading items.
   
   
2. Does the game let you level up?
   
   
3. Does the game have the element of collecting items?
   
   
4. Is the game play micro-gaming-like?

This is important as users today don't have long attention spans. This is especially true on the net as there is just just too much things for the users to do: watch a YouTube video, Twitter, chat, web surfing, using other apps. The key is letting the game be played in a short time interval across multiple sessions. In other words, short sessions and not long sessions like home console games.

That's all for now. Thanks for reading, and what other critical factors are there to making a successful social game?