The PlayBook was officially the first BlackBerry device to ever be jailbroken when a tool called Dingleberry came around. Because of it, many people have wondered what RIM's stance on it is. In a post to the Inside BlackBerry for Business Blog, Adrian Stone, Director of the BlackBerry Security Incident Response Team (BBSIRT) at Research In Motion, explains the cons of jailbreaking your PlayBook. The biggie being that it actually void your warranty with the manufacturer.
To be clear, RIM recommends against installing any jailbreaking tool. Customers who use a jailbreaking tool on BlackBerry products void the manufacturer warranty and also increase the long-term risk of negatively impacting the stability and user experience of their BlackBerry products. Use of a jailbreaking tool could also amplify the impact and severity of a future security issue, making your personal data more vulnerable to theft and more difficult to protect. If new jailbreaks for BlackBerry products are reported, rest assured that we will evaluate them and take appropriate action to help protect customers.”
Since BlackBerry 10 will be heavily influenced on what we have in front of us as PlayBooks, it's no surprise the RIM would want to address this as quickly as possible. BlackBerry 10 devices will probably be jailbreakable too if they can't figure out a way to prevent it before they are released. Only time will tell.