An old trick is to use abuse the crawler to generate a huge index for reverse lookups. For example, reverse "72b302bf297a228a75730123efef7c41" to md5("banana").
Probably not. Googlebot likely has very fine-grained limitations on CPU/memory/IO usage, and penalizes websites that use too much. Just a hunch.
This could work, especially on high-ranked news sites that are crawled every few minutes for new content.
I just noticed a comment on HN that I wrote a few minutes ago, was already in Google search results - was shocked a bit.
They're indexing blog posts and content within seconds, not minutes. I've seen my blog posts indexed within seconds and they've been doing that for a few years now.
The best way to achieve this is with PubSubHubbub to avoid the delay of polling your feed or pages. (Not that it would necessarily stop.)
That's probably because a default wordpress install has pingomatic.com listed in the callbacks for on-post ("update services").
I had a not-important site with many pages, for a while Google was crawing it continuously, with 10 threads in paralell.