I generally put into this category programs
that use words like Automatically
, or some such.
If a program, is, say, trying to automatically enter in the information you need for every web form you fill out, it will basically go crazy with every permutation of field name, size, format, etc that even if it gets 90% of them right, it will inevitably fail, and fail often, probably on the things you want it to work the most. Such software can work fine, on, say, a single vendor's website, but to control all possible ways of entering data and displaying fields without any standards means sure disaster.
This is also true of virus scanners, Windows 98 when it attempts to optimize your hard drive so programs load faster, digitalme which attempts to fill out all forms, Internet Explorer's AutoComplete which does the same thing, any creepy expert that tries to figure out what you will like based on what you do like, and internet filtering software. I'm not saying these things will not work at all, but they will never work completely. In fact, sometimes you can't even define what working completely would be.