This isn't the best way to describe the problem or solution.
Users can be advised to install an ad-blocking plugin for their web browser to protect themselves. Since Google serves adverts from domains other than google.com, users can continue to use the google.com domain for search while at the same time blocking the malware coming from ad networks.
Looks like a bunch of static assets delivered by:
fonts.googleapis.com, fonts.gstatic.com, pbs.twimg.com, and www.youtube.com. Looks similar to what I saw post-defacement/pre-fix.
Not really. A defaced high profile website will draw visitors e.g. from all major news sites, maybe even TV. Combined with a couple 0days or a browser exploit kit, quite a chance to infiltrate a target.
And if you're lucky the online reporters also have twitter/fb account info on their PCs. I guess this is how the various compromises of twitter accounts have been done.
[1] https://news.ycombinator.com/item?id=8879229