Google adsense showed an error page just this Saturday past. It didn't last long I'm sure, but it (EP) was there.
I've seen google.com down for a few minutes a couple of years ago. I used google.co.uk, and it worked fine
It just happend to me recently few weeks ago. Google wouldn't load youtube would not load but every other website would open with a blink of an eye. Sometimes if you search for hours and hours on google and you click on the sponsored ads constantly they block google on your IP automatically for few hours or a day, because google take that action as a fraud clicks. I just refreshed my Ip and it worked again and I wasn't doing it on the purpose I only clicked on the links that were related to my topic.
there is saying "If something can go wrong, it will go wrong" so It could happen- "Google Down" Probability of it is Less than 1 BUT greater than Zero
Never been heard about this before that google server is down for a single second they are perfect and up 24/7.
I have never seen such situation with the Google as I have seen such message or something like that that Google serve is down for maintenance or anything. Ya but I have faced many times search query disturbing message. As I was checking my some targeted keywords of some site in Google and after just checking 30 to 40 I got message that we are Sorry.... Unable to process your query. But that time was for Google back link updation and there may be a problem perhaps of the database from where search queries are coming.