Here is an obviously bent fork example:



Note how close the front wheel is to the down tube. Somehow I missed seeing the bent fork in the thrift store because I was distracted by the FFS system and broken shifter and wondering if I could fix it or not. I spun both the wheels and looked for straightness, and even checked the deraileurs, but didn't notice the fork until I was putting it on the car. Funny thing about this is that front wheel is currently in service on a friends bike. The frame and fork took the hit, yet the wheel survived and stayed true and round... ok well true and round enough to keep using.

Here's one that's less obvious:



The bike had been in an accident, it seemed fine for the rider but then while out riding the top tube bulged, the down tube wrinkled and the tire went back into the downtube. It's more difficult to tell from the picture, and often a picture like this is all you get from an ebay or CL ad. The fork looked good to me at first, however it is bent. It's a pretty chrome fork and if I end up having a use for it, I may try to bend it back. The frame however is now wall art.