I'm curious how this bug will affect bitcoin price. I'm betting it'll go up even more.
This should be a wakeup call for anyone that thinks that Bitcoins are totally secure. What if next time the bug in the client is more exploitable? Someone malicious could potentially take out the entire Bitcoin economy in one day by exploiting it.
Like every other system, including the existing ones, it'll have to get better as it scales.
You only need to notify miners and mining pools. These have been concentrating for a while and will continue to concentrate in the future.
Individual users who aren't mining don't need to do anything.
Users could be warned to STOP using v0.7 and upgrade to v0.8. The advantage of downgrading it is resolve the situation quicker. Far easier to get a half dozen mining pools to switch to v0.7 then get thousands (tens of thousands) of users to upgrade to v0.8. A v0.7 user who followed the warning and stopped engaging in transactions either until v0.7 was the longest chain or until they upgraded to v0.8 was not in any danger. Existing transactions flowed across both halves of the split.