Google's John Mueller said in a Google Hangout yesterday on Google+ that it is really rare Google wouldn't be able to find content (with the exception if it is blocked by you) that is accessible on the web.
He said this at the 15:43 mark into the video. He said:
Yeah. That's one thing that sometimes you you need to watch out for. But I see that really rarely, that we don't find content at all.So it's something that sometimes comes up in the forums where people would say why doesn't Google index page, I added this to my site like a week ago, why isn't showing up. And it's almost never the case that I look at that and say oh your internal linking is bad. That's really really, i don't know maybe I've seen like two or three cases in the last year, where I can say well the internal linking of the site is is problematic.
For the most part it's really, if you have a modern CMS, normal setup then somehow we'll be able to find those pages. Obviously we can do better if you kind of move that higher up the chain but for the most part we we can find it. And obviously there are things you can do to improve that, where you can optimize it and make sure that it's easier crawlable or harder crawlable.
Two or three times he saw a case of this in the past year, that does seem rare.
There have been some people asking me if Google is having issues recently finding new content but the reports of this are very very limited. Maybe one or two people asked me but I have not seen mass complaints.
Here is the video embed at the proper time:
Forum discussion at Google+.
