One of the problems we are still facing in the world of information security is that people still have a built in tendency to trust authority figures. If it looks "official" enough, most people will trust it and follow, like lambs to the slaughter. This caused the infamous "MS Antivirus" nag ware to be so effective - it's made to look like it was made by Microsoft, and most people just trust it and believe it's real.
A more interesting, and frightening case of being fooled by software is illustrated by the tale of G-Archiver. This free utility is designed to allow the user to backup his Gmail account to his local computer. Generally, this is a good idea, as one never knows when his account might be frozen or accidentally deleted. In this case, however, it has been discovered that the program works in a way that's insecure, to say the least, and borderline identity-theft. Apparently, the software is coded to send an Email back to its creator, with the credentials of any user who uses it (you are required to give it our credentials, so it can download all your message for backup). A programmer who investigated it discovered that the developer's Gmail account was full of user+password info for thousands who downloaded the used the program. Even worse, it also turned out that the developer embedded the credentials of this account (where the passwords are being sent to) in his code, so anyone with the right skills can access it and harvest all these users-names and passwords.
If you are one of those who used this software, now would be a good time to change your Gmail password. In fact, it's a good idea to change it once a month anyway, although I don't fool myself into thinking that any normal person will actually do that. Well, I hope that you at least change your PayPal password now-and-then. What's frightening here is that most of us, even experienced Sysadmins and security experts, trust programs we download to do what they say. Few, if any of us, check if a program contains spyware, and few have the skills to check for the kind of behavior mentioned above. Your credentials or private files could be circulating all over the net without you even suspecting it. On a similar note, many people install file sharing applications and share their entire drive, without realizing that all their personal documents are readily available for everyone. Want proof? Open up some file sharing program and run a search for "my cv.doc" - you will find many!
Some organizations have configured domain-enforced policies that prevent installation or even downloading of unknown software, but that's only been done within a handful of companies. If your org considered it, it was most likely rejected for political reasons - it's not easy telling everyone that they can't install anything on their computers anymore - it sounds fascist, doesn't it? If you ask me, this is already a necessary step right now, and it's only a matter of time before more security administrators or CEOs realize it and make it happen. At home, it's even worse as there are no mandatory settings. We have the technology to sign software by a trusted publisher, but hardly anyone uses it. Perhaps it's time, before the next wave of a Conficker-like worm hits all of us?