During the latest Webmaster Hangout, Google spokesperson John Mueller answered a question about problems with thin content. According to him, this usually refers to the site as a whole, and not to any specific pages.
“Usually it’s more about the site as a whole. So it’s not so much that there isn’t enough content on one page, but rather that the resource as a whole contains very little relevant information.”
SearchEngines concludes that if Google fixes a problem with non-informative content, then this applies to the entire site, and it needs to be solved at this level too, and not just page by page.
As for the specific number of words that should be contained in the text to make it informative, Muller lamented the SEO industry’s obsession with this issue.
“I would hate to use word count as a way to recognize this. I think sometimes word count can be useful for webmasters to look at the content of larger sites and compare it to theirs to find areas where they can do better. But I wouldn’t use word count as a guide to specific actions on the site.”