Considering how many Android devices there are, it is likely that Google can access most Wi-Fi passwords worldwide.
Recently IDC reported that 187 million Android phones were shipped in the second quarter of this year.
That multiplies out to 748 million phones in 2013, a figure that does not include Android tablets.
If I had an Android phone or tablet I would send this to Google: "My password is “NSA-loves-Google.”
Nothing would come of it but then neither would sticking my tongue out Google.
Full report with specifics here.