Zynga gets a freer hand to operate a standalone gaming website, but gives up its ability to promote its site on Facebook and to draw from the thriving social network of about 1 billion users.
"Although Zynga investors have reacted negatively to Thursday's announcements so far, we view them as a long-term positive for both companies," Wedbush Securities analyst Michael Pachter said in a note to clients.
"Zynga now has an advantage to offer more payment options which could result in additional subscribers who are not Facebook users," he said, maintaining his "outperform" rating and price target of $4 on the stock.
Both internet companies have been trying to reduce their interdependence, with Zynga starting up its own Zynga.com platform, and Facebook wooing other games developers.
In recent quarters, fees from Zynga contributed 15 percent of Facebook's revenue, while Zynga relies on Facebook for roughly 80 percent of its revenue.
Francisco-based Zynga's shares were down about 7 percent at around $2.44 in morning trading on the New York Stock Exchange on Friday.
Facebook shares were down more than 1 percent at about $26.98.