Social gaming company Zynga, which opened in December at $10 per share, has seen its stock fall below $5 for the first time, as traders believe fewer people are playing games on Facebook.

Reuters reported Tuesday that the stock value of Zynga — the producer of popular games such as FarmVille and Draw Something — hit an all-time low of $4.78. Analysts feel that as more people play games on their cell phones, fewer visit Facebook to get their gaming fix. Daily active users fell 8.2 percent to 54.2 million in May.

The company was originally valued at $9 billion when it launched its IPO in December, but it has since shed about $4 billion of its value.

Insiders also feel that the way Facebook’s stock has tumbled since its much-hyped IPO has had a negative effect on Zynga. Nasdaq has halted short sales of Zynga stock — a ban that will last through Wednesday.

Cowen & Co. analyst Doug Creutz told Reuters:

We believe that interest in Facebook-based gaming may have reached a negative inflection point as more casual gamers migrate to mobile platforms.

The news of Zynga’s falling value comes not long after the game developer saw great success in the first quarter, thanks primarily to Facebook. In that first quarter, Zynga reported 65 million daily active users and a revenue stream of $321 million, a 32 percent gain compared to the first quarter of 2011.

Zynga has been trying to reduce reliance on the social network, finding other ways to get people to play its casino-based games. The company was trying to partner with gambling websites in an effort to make the games more profitable, as Facebook doesn’t allow gambling for cash.

Readers: how often do you play Zynga’s games, and do you prefer to do so on your phone, computer, or tablet?