Such an armada might not, however, be necessary to produce a more modest but still useful effect.

ECONOMIST: Fiddling with clouds could help tame hurricanes

This, in turn, could have a useful knock-on effect.

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If financial engineers have their place in bringing about useful change, consider the effect of business-process innovators.

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This, too, can be hyperpolarised but, unlike 3He, it can also be absorbed by blood, and can thus get into the rest of the body, an effect that may be useful for other types of diagnosis.

ECONOMIST: Medical imaging

The close juxtaposition of these disclosures has generated much useful discussion about secret stakes, their effect on the market, their effect on companies, and what changes or regulations can or should be mounted to address their potentially deleterious impact.

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Google considers these non-GAAP financial measures to be useful metrics for management and investors because they exclude the effect of SBC and as applicable, one-time events so that Google's management and investors can compare Google's recurring core business operating results over multiple periods.

ENGADGET: Google's Q4 2011 results: $2.71 billion profit, $8.13 billion in revenue, Wall Street disappointed

For a bubble to have a genuinely valuable lasting effect, it must do something more than construct useful things wastefully.

ECONOMIST: Booms and busts

What Google gets from Buzz is a new means of organization, one that should make Google an even more useful part of life--with the not-incidental effect of improving its ability to sell advertising on its search results and mail.

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The focus may be narrow, but the effect is not trivial: telling people how to influence their local school or hospital is useful and gives them real political power.

ECONOMIST: Here is the news