RTFA: http://arstechnica.com/news.ars/post/20070523-rese…

“Last time, it took nine years for us to generalize from a special to
a nonspecial, hard-to-factor number,” Lenstra said in a statement, referring
to a 155-digit number that his team had broken previously. More recently,
a 200-digit non-special number was factored in 18 months and roughly 50 years
of computer time. This 307-digit crack took even less (human) time, which
Lenstra credits to more powerful computers and improved code. “I will
not make predictions [about the future of 1024-bit encryption], but let us
just say that it might be a good idea to stay tuned.”

Why does anyone care? While your average Joe or Jane on the street will not
be able to crack a 1024-bit RSA key anytime soon, experienced attackers might
not have such a hard time. Getting the computing power to crack a 1024-bit
key could be as easy as employing a decent-sized botnet
or two.

Someone clicked to RTFA after searching for “rsa bot net crack.” I saw that and realized it’s an insanely cool concept. Lo, the idea has been floated before.