A shorter version was published in the inaugural issue of the British edition of Wired vol. Both procedures carried risks. I hope that nobody intercepted my unencrypted message. More importantly I trust that the blood donors were healthy and the testing procedures thorough. They know that should they themselves ever need blood, supplies will be available thanks to the actions of other, like-minded individuals.
Contributors get personal satisfaction and possibly prestige.
They also know that they will be able to obtain information in the same way when they need it. The golden rule works and what is good for others turns out to be good for the individual. The reverse can also be true. However markets do not always work to everyone's benefit. Booms followed by slumps have been caused by speculation in everything from tulips to shares.