As if you didn't have enough things to worry about, check out Michael Horowitz's article at Computerworld:
Google knows nearly every Wi-Fi password in the world
If an Android device (phone or tablet) has ever logged on to a particular Wi-Fi network, then Google probably knows the Wi-Fi password. 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.
Many (probably most) of these Android phones and tablets are phoning home to Google, backing up Wi-Fi passwords along with other assorted settings. And, although they have never said so directly, it is obvious that Google can read the passwords.
Sounds like a James Bond movie.
Android devices have defaulted to coughing up Wi-Fi passwords since version 2.2. And, since the feature is presented as a good thing, most people wouldn't change it. I suspect that many Android users have never even seen the configuration option controlling this. After all, there are dozens and dozens of system settings to configure.
And, anyone who does run across the setting can not hope to understand the privacy implication. I certainly did not.
Read the rest here: http://blogs.computerworld.com/android/22806/google-knows-nearly-every-w...
Oh, and change your wifi passwords now. You'll be completely safe until the next device logs in...