[p2p-hackers] cellcash

[Lucas Gonze]

http://www.nytimes.com/2005/08/25/technology/circuits/25pogue.html?pagewanted=2
...
To prevent spammers and other abusers from snapping up Gmail accounts by 
the thousands, Google has designed a clever safeguard: when you apply 
for a Gmail account, you must provide a cellphone number. Google sends a 
code to your phone, which you use to complete the registration.
...

This is hashcash, almost, except that what it uses for a backstop isn't 
CPU time but the fact that cell calls are always metered.

Those Google fellows sure are clever. 

- Lucas