Some decades ago there was considerable, and appropriate, concern that the use of certain chemicals (some refrigerants, and some used in aerosol sprays, which were all primarily chlorofluorocarbons or CFCs) was causing the layer of ozone in the upper atmosphere to thin, thus reducing the protection against harmful wavelengths of radiation from the sun that the ozone layer provided. There was much talk about the ozone hole and ozone depletion. Steps were taken internationally to ban the production of CFCs and by and large these steps worked. Alternatives were available, and substitutions were made at relatively low cost.
So the ozone hole problem went away, or at least diminished in importance. Except, recently there has been speculation that removing the ozone hole (restoring the ozone depletion if you will) may have contributed to global warming! Clearly, stopping the use of CFCs was the right thing to do, but that action may have had the undesirable result of adding to global warming. And unintended consequences are common in many areas of technology use and development.
However, the unintended consequences are not always bad news. Two recent examples may help to show this.
When the iPhone and other smart phones were in development, I very much doubt that the developers imagined more than 10% of the various ways in which people would use them. Some ways, to be sure, are quite frivolous, but others can quite literally save a life. One such example is an application (called the muTec) whereby a suitable smart phone can be transformed into a friction measuring device. This can easily measure the friction on the road while you are driving. That value of friction can then be sent (along with GPS location information) to a web site with a map, and the information is displayed there and can warn other road users of potentially low friction locations on the road. This technology will have a profound impact on all those folks who are busy removing snow and ice from the road here in Iowa and elsewhere in North America and around the world. The price of the application is sufficiently low (about 400 Euros) that agencies would be able to afford sufficient of these to provide a very accurate picture, in real time, of the slipperiness of the road system. That will save lives and improve mobility, and I very much doubt that those smart phone engineers were thinking along these lines!
Likewise, I suspect that the inventors of ARPAnet, which is the grandparent of the Internet, were not thinking in terms of wiping out corruption when they were writing their code back in 1969. But today, some smart folk at 5th Pillar, a non-governmental organization (NGO) in India, have been doing just that, by providing on the Internet a zero Rupee note for downloading and printing. People in India have then been giving these notes to corrupt officials who want a bribe, and the results have been remarkable. It turns out these corrupt bureaucrats are indeed embarrassable, and a zero Rupee note does the trick wonderfully. A simple idea is having some profound, and definitely good, consequences!