Google's John Mueller was asked in the Google+ Hangout at the 14:05 mark about lazy loaded content, specifically on mobile. Can Google see all that content and the quick answer is no, Google cannot load all the content within the lazy loaded content - be it mobile or desktop.
But the same is true for mobile only sites. Google has a hard time finding content when that content is loaded after you scroll.
Does google crawl and give same importance to the content which is lazy loaded on mobile, i.e. we keep loading the content as user swipe the screen down when on mobile device.
That’s tricky. So if we have the full content on the desktop page, then we would probably take that into account and use that also for ranking them on mobile.
If it is only a mobile page and the content only appears where you swipe down, then chances are, we most likely won’t be able to see all that content. The main difficulty there is that when GoogleBot loads a page, it doesn’t really know what to do to make all of the content appear, if it has to do something specific.
That is in regards to clicking on tabs, then it loads content. Or in regards to swiping in a certain way, from a direction, from a certain place, all of these things are really hard for us to kind of know what GoogleBot should not to kind of be doing.
So that is something where I’d recommend using the fetch as Google tools to kind of see how far Google sees the content, does Google see enough of the content or is there something missing. Because what we sometimes see with pages like that is that they sometimes use some type of infinite scrolling, where you can keep scrolling to see more and more content. If the additional content is content we indexed separately anyway, then there is not like we are missing anything anyway by just indexing the first page.
So that is kind of the situation where you kind of have to think about what content am I providing, is GoogleBot able to see all of that, and if so, maybe it doesn’t matter if GoogleBot can’t keep loading when you swipe up.
So in short, Google really can't index that content, so you need to test to see what Google can index using the fetch as Google tool.
Here is the video embed at the start point:
Forum discussion at Google.