Proprietary vendors are using "anti-features", features that no user would ever want, to protect intellectual property, Benjamin "Mako" Hill, from the Massachusetts Institute of Technology, told the linux.conf.au open source conference last month.
But IP protection is only one of several reasons vendors introduce such features into their products.
An anti-feature serves the interests of the vendor, he says, not the user. A typical example is the set of limitations placed on the Home Basic version of Microsoft's Vista operating system; these restricted memory and disk-storage support and limited the user to at most three concurrent applications using the graphical user interface, Hill says.
"The aim was to make it so bad that anyone would pay to upgrade to the next version," he says.
This is the strategy of market segmentation -- the creation of classes of user who pay different prices for what is essentially the same offering.
Often the anti-feature is used in a naked effort to extract money directly from the user, Hill says. A number of software products, even whole PC systems, come in two versions; the more expensive one without the spyware. He compares this to protection rackets and the long-established practice of paying a fee to have your phone number excluded from published directories to avoid nuisance calls.
Anti-features are also used to preserve monopolies or enforce copyright. Panasonic, he says, once promulgated a "firmware update" for its cameras -- since removed -- the sole purpose of which was to stop the camera working with a third-party battery.
From the hardware dongle to digital rights management software, there is a major effort throughout the digital market to "make computers into less efficient copying machines", he says.
Hill portrays anti-features as a characteristic of the proprietary digital marketplace. With free open source software, the tricks are very quickly detected and removed by smart users.
Promoters of free open source code nowadays put more emphasis on the "open", says Hill, "because the word 'free' scares anyone in a suit". But the anti-feature question shows that freedom to read and amend code is still a fundamental benefit of the open source movement.
In conversation after Hill's session, however, some attendees questioned whether open source still excluded a large number of users -- those who are not geeks or "hackers" and who do not know the right person to approach or a trustworthy source to go to for a fix to remove or work round an anti-feature.