Reasons that are beneficial for utilizing software which is meant for portability is the ability to use a simple USB device. Not only does your system prosper from the use of portable applications, you have the ability to turn your USB stick, or any USB enabled device such as an iPod or Zune, into a PortableApp Suite. For example, PortableApps.com Suite™ is a collection of portable apps such as a web browser, anti-virus, and more—all of which can be launched via an integrated menu configured for portability. When finished with the host computer—if the programs are properly made portable, then there shouldn't be any trace of your existence or usage of the system left behind on the host PC.
Portable application suites like PortableApp.com Suite™ and LiberKey have a huge community dedicated to to the development of portable applications. Communities like reboot.pro and virtuliztion from VMware and Oracle, give you the ability to completely transform your entire PC environment into a sofisticted set of portable, virtual, take-anywhere-you-need-to-go utility.
Some Common Problems
A common problem with most installed applications is it's completely dependent on the Windows registry file-system. Most applications rely on the original PC which it was initially installed upon. Typically, if the program's author wrote the application as such the software's configuration and settings are fanned out in many folders hidden (or otherwise) from the user. Which in turn hinders the ability to backup your applications settings/configuration from unforeseen mishaps such as "the blue screen of death" or hard drive corruption. So when you need to reinstall said program, or dare I say it, reinstall Windows itself, all your settings and your personal data are either lost or corrupt and you'd have to reinstall/reconfigure every application you had prior. Most programmers have you purchase their software and the ability to reuse these applications if you, worst case scenario, loose all your data, it is damn near impossible due to licensing issues leaving you to purchase their software again.
Besides the added perks of not having to install a program onto your computer and booting a virtual PC from anyone's computer anywhere, one does not experience performance degradation over time with portable programs. The idea of portable applications are that they've been designed to avoid getting threaded into any one particular PC. If properly wrapped (or virtualized) the application should have all it's configuration files and registry entries stored within it's launcher's directory or sub folder. The possibilities are seemingly limitless. So if you're constantly moving from one PC to the next, you can take your most beloved software and/or virtual system with you and access your content on any host PC. So let your inner-Geek play around anywhere and everywhere with you're favorite software, made portable alongside a portable machine.