lucy24 - 7:16 am on Jul 24, 2012 (gmt 0)
Yup, it's a file with a nonsense name-- except that unlike the ones g### has been looking for recently, the authentication file's name is mixed alphanumerics. If you have file-upload access to someone else's site I guess you could easily claim to be the site's owner for gwt purposes. Don't know how else you'd do it.
Now, if googlebot were a human in a certain age bracket, it would turn out that it had simply forgotten the name of that authentication file and was wildly guessing in hopes of hitting the right one. But, even at the minimum range of ten lower-case letters, the odds of guessing right don't look good. (Calculator says it's a 15-digit number. I'll take its word for it.)