Speaking of tourist disasters in SF; when I was there back in May, there were a few blocks somewhere around (IIRC) Post/Van Ness where the GPS in my Galaxy Nexus would actually pick up a mile or so off from where I actually was. Realized what was happening right away and still know how to read maps[0]; but could easily be a problem for anyone who isn't paying attention to everything.

[0] Semi-related: whoever decided to stamp street names into SF sidewalks: thank you.