You only need to have a look through the winners list to see examples.
There are also those who win using multiple names and aliases, yes, I know folk do this, but I decided years ago that I could not thoroughly screen such multiple entries and just accept that some folk feel the need to do this in an attempt to win the prize. It's usually found out when I ask to whom the cheque or Paypal payment is addressed to!
The Daily Entry Competition is drawn randomly from all the correct entries, so odds are that
people will win several times over the years that it has been running since 2002. Such odds are reduced when it comes to the
Caption Photo Contests and here again a winner won several years in a row because his comments
were so funny and were chosen by the judges, who do not get to see names, just the captions.
Compers think that some promoters don't choose the same winners again, but I'd argue that most run their contests fairly and just want to see many entries and a fairly awarded prize to a grateful recipient.
So, I'd recommend keep entering my contests, and then one day, it could be you who wins!