All your personal data is keyed to your own assigned bib number. At many races, results are delayed because people have inadvertently switched bib numbers with their children, spouses, team mates, friends. Once you pass over the finish line . . . The tags are stacked in order of finish, then matched to the times recorded at the official finish. Finish times are all knocked off by one place each time this happens.
Most races have staff to assist at the finish line area.
Others have paid a fee for this, plus the timers are going to record you when you cross the finish line. Time waits for no one. Buy books, magazines on the sports you will participate in. Try to remain calm and voice your problem, complaint, or suggestions clearly. If you have enjoyed the event, have realized how hard so many worked unpaid, saw how many people cared for your success, and have given their best .