Proposal: Pre-emptive measures against 51% attacks

[DeathAndTaxes]

Asking again because I think this is very important, especially because of the 25 BTC change at the end of the year, many legit miners will leave and the bots will remain, thus making Bitcoin vulnerable to a 51 % attack.  Gavin and others, any progress or information on this?

Why would the network be more vulnerable to a 51% attack by botnets then "legit miners"?  Hashing power is hashing power.  Botnet operators profit (unethical or not) be keeping the network secure.