In today's hi-tech world, where every T, D and H owns a laptop and more, a fully equipped pen drive still makes a lot of sense.
Top 5 scenarios where a pen drive loaded with the rights apps makes great sense are:
1. You regularly work on a set of files on different computers (one at the office, one at home, one on the go blah blah blah...).
2. The "friendly" neighborhood sysadmin has forbidden installation of software on the office machines.
3. You are going on a well deserved vacation (and you obviously don't want to lug the laptop around) .... but you need to carry important files in case there is an emergency and you need to work from a cyber cafe.
4. You need to backup files (pen drives are smaller than CDs and DVDs).
5. You want to carry some great videos / movies around.