One of my colleagues from work:
- Looks through the code and finds a chunk of code that looks fishy (to her)
- Sais that she never understood why it was implemented that way
- Deletes the chunk of code
- Starts rewriting it
- Remembers why it was done that way
- Reverts it back and moves on to something else

Just why? It would have taken her 1 min to read the code ...