A Facebook-PayPal partnership announced last week will allow Facebook Messenger users to link their PayPal accounts and send and receive money without leaving the site. But beyond that seemingly innocuous feature lies a cleverly crafted survival strategy at both companies, says Wharton marketing professor Z. John Zhang . Much depends on whether both companies play it right in integrating the service and making it easy for users, says Jennifer Golbeck , director of the Social Intelligence Lab and professor of information studies at the University of Maryland. Facebook could “push people towards this idea that Facebook is a place where exchanging money is common.” Both experts also saw the partnership as an example of a “grand convergence” occurring in the digital world and potentially a precursor to other big acquisitions. Zhang and Golbeck discussed the Facebook-PayPal partnership on the Knowledge at Wharton show on Wharton Business Radio on SiriusXM channel 111 .…