Fot the second time in the last 2 weeks and 4th time in the last 6 months G de-indexed my homepage across all the DC's while keeping all the others. Each time it lasted 12 - 24 hours before the page was back across all the DC's. The odd thing is that every time it happened I had a significant boost in traffic from G when my page came back, while no major loss while it was gone. De-indexing can be a good thing.
They don't. You connect to different data centers all the time. They have some that they use for development and testing. Sometimes you see a flux for several hours or days. A lot of times people will see their index page get indexed, then it stops showing only to return in a day or two.
My home page disappeared from all the data centers, not just 1 or 2. I can tell when it happens because there is no traffic to my home page from Google at all, just to sub pages. I can also tell when it starts to get indexed again as traffic to the index page slowly starts to trickle in till it's back to normal. Luckily when this happens my sub pages take over in the SERPs.
Very interesting, never heard of such a thing! Probably your homepage is eclipsing the SERP of the sub-pages.
How often does it happen? It might be a complete crawl so they put the old crawl in cache and crawl the whole site again. I guess you get high traffic.
I don't use tham. It happened about 6 months ago, then 3 months ago, now twice in the last 2 weeks. Yes, I get decent traffic. When the page get's reindexed it comes back as mysite.com/index.html for a while before finally reverting to mysite.com.