Hi, it's Will. We are all probably annoyed by software that bundles other applications that we didn't ask for. You want a specific application, but depending on what the application is, where you downloaded it from, and how carefully you paid attention to the installation process, you could have some extra goodies that came along for the ride. You might have components referred to as adware, foistware, scareware, potentially unwanted programs (PUPs), or worse. Sure, these may be annoyances, but there's an even more important security aspect to these types of applications: attack surface
more here..........http://www.cert.org/blogs/certcc/post.cfm?EntryID=199
more here..........http://www.cert.org/blogs/certcc/post.cfm?EntryID=199