A little bit ago I received an updated eTicket receipt from United for a trip in Novemeber. But I was a bit confused since this new itinerary was for a trip to Chicago and back and I had no plans (at least that I remembered) of going to Chicago.
After a bit of digging, I realized it was for a trip to Portland, OR. What's interesting is that my routing had been EWR-PDX-ORD-LGA yet somehow the system thought I was going to ORD.
So I rang the 1K desk and the agent was as perplexed as I was, but she rebooked the proper flights and had to wait for it to be reticketed. Fortunately, since the wait was a bit long, she offered to call me back after getting it all resolved.
In all my years as a CO flyer, I've never seen anything like this happen so this was definitely a new one. So pay close attention to any updated receipts you get and make sure your destination is still the same. :)