I don't profess to being an expert on this issue - but it's a bit more complex than simply "We don't work at X files". There's a bunch of factors, including the user's own environment, and lengths of certain fields that can affect what the exact limit is. Memory is a moving target.

Other clients exhibit similar behaviour - e.g. Dropbox states a limit of 300,000 (https://www.dropbox.com/help/space/file-storage-limit), and from my own informal testing, I know Box.net also exhibits odd behaviour as well.

(Disclaimer: I work for Google, but the above comments are purely my own).