Some unscrupulous ne'er-do-wells have capitalized on Rovio's latest release. A Google Chrome plug-in claiming to be a free PC version of Bad Piggies actually installs adware, and so far more than 80,000 users have been impacted.
The security firm Barracuda Networks (via Joystiq) tested out several fake Bad Piggies apps, many of which came from a single source called Playook. Installing the app gives a prompt to "access your data on all Web sites." If you grant it permission (which you definitely should not do) it then populates sites with ads. The greater risk of giving such a permission is the possibility of giving over sensitive information like credit card numbers or passwords.
Most who follow the games industry closely would probably know better than to install a suspicious "free" app into Chrome. But it couldn't hurt to give a heads-up to your non-gaming family and friends, lest they fall into the trap.