Parisimonious design is when you’ve got enough, but no more. It prefers simple solutions to complex ones and conserves scarce resources wisely. We might think of these resources in economic or environmental terms and design products that are both cheap and don’t consume an excess of material or energy. We might consider the user and reject designs that squander their time, attention, energy and space.

Many bad designs offend against the principle of parsimony by being too big, too wasteful, too expensive, too complex, too high maintenance. Such designs are the metaphorical sledgehammer to crack a nut. We find ourselves thinking, “Do we really need all this just to do that?”

Two relatively new products should provide cautionary tales.

The Segway PT has been in the news lately as various parliamentarians including the peculiar Lembit Opik MP have put their slender weight behind a campaign to legalise their use on Britain’s streets. Clearly the fact that the Segway is currently illegal both on the roads and on pavements in this country must put a dampener on sales. Yet I suspect that even if some form of legalisation is eventually forthcoming, the Segway or anything much like it won’t become a significant mode of transport in urban areas.

The Segway does well in packing some seriously complex technology behind a relatively straightforward user interface, but my instinct is still that it’s overdesigned for the tasks it’s supposed to serve. Employing a £4000 electric vehicle just to be able to travel a little faster than walking or a little slower than cycling and in many cases with less range doesn’t offer enough marginal benefit to be worth the price, let alone the trouble of having to charge, insure and maintain it. As indefatigable campaigners Living Streets keep reminding us, walking two or three miles for everyday journeys is often much quicker and more pleasant than we might imagine, particularly when compared with the alternatives. We’re just not in the habit of doing it. For those that want to travel further or more quickly, a £50 bicycle beats the pants off vertical milk float technology in almost every respect bar sloth.

So whenever I see Segways now I can’t help but be reminded of simpering Mr Opik proudly standing eight inches above a group of bored journalists selling the idea that his dorkmobile stands between us and ecogeddon as if his life — and ours — depended on it. Not parsimonious, I’m afraid. Move along.

This week sees the launch of Sony’s latest ebook reader, the imaginatively-titled Sony Reader (PRS-505). The Sony competes with Amazon’s Kindle, forthcoming wizardly wonders like the Plastic Logic Reader and, well, books.

Despite — or perhaps because of — my love for good old fashioned dead tree books, I’m instinctively drawn to the idea of an ebook reader in almost equal measure to how I’m repelled by cumbersome personal transporters. Ebook readers promise to lighten our loads and cut clutter by replacing paper books with ethereal digital equivalents in much the same way that MP3 players have eliminated the need for CDs and vinyl for many. Is this parsimony?

The environmental credentials of ebook readers are hard to guess, but I’m sure they can be calculated. On the downside we have a (say) £200 device with complex electronics and a lifespan of five years, to be generous. On the upside, we have the lack of dozens or hundreds of paper books per device, their storage, transport and ultimate disposal. If the device really does provide an adequate substitute for paper books, I could be persuaded that it has environmental and space-saving benefits.

But there’s the rub. As the designers of the original Palm Pilot found, competing against the speed, flexibility and cheapness of paper is tough. Moleskines are the new PDAs. In The Myth of the Paperless Office, Sellen and Harper offer a compelling explanation of the obvious: Digital technology has increased rather than decreased the amount of paper in use and this trend looks set to continue for the foreseeable future. The things that paper does well, computers do not. Further, computers have stimulated and expanded the various kinds of knowledge work in which paper is an essential tool.

So are ebook readers parsimonious? Could they be? At the current state of technology, ebook readers are adequate for linear reading but very little else. If you’re addicted to airport novels they could be right up your street. But the complex browsing, cross-referencing and annotation that is commonplace with professional and academic reading is way beyond current ebook readers’ capabilities. Moreover, it’s usual for students and professionals to refer to several books and documents at once, implying that for this kind of use, the ebook reader is competing not just against one simultaneous book but several. It’s no consolation that your ebook reader may have the capacity to store 6000 copies of War and Peace when what you really want to do is to refer to all of Tolstoy’s works at once. If £200 for an ebook reader sounds reasonable, try budgeting for a dozen of them.

While ebook reader technology will presumably evolve to incorporate more of the characteristics of paper and thereby gain paper’s flexibility and affordability, right now the most parsimonious way to use large chunks of text is to print them on paper and bind them into attractive and durable covers. You can’t compete with tree.

The Segway and ebook readers condemn themselves to whimsical or niche uses by flagrantly ignoring the parsimony principle. Between two designs for the same purposes, the simpler one is the better one.