In the extreme, the image of your child could be used in an advertisement for infant formula or nappies without you being consulted or paid. Your lanscape photo could be sold to advertising agencies across the world without you receiving a cent or acknowledgement as the photographer.
Would you give your best photo as a gift to a stranger?
How do you protect yourself and your images when entering competitions? In short, always read the Terms & Conditions so you understand how the competition organiser may be able to use your images. Key terms to look for include:
"royalty free "
"without further permission"
"without further compensation"
Now this can all be very confusing if you're not trained in the law (and I'm not). For expert information, take a look at the sites below.
Pro Imaging - Rights Grabbing, What Is It?
Article in The Australian newspaper: Negative exposure over rights for photo contest
Arts Law Australia: Legal Information for Visual Artists
Artists Bill of Rights approved competition list and Competition Notices
For competition organisers: sample Terms & Conditions from the Artists Bill of Rights website
Here's what photographers are saying about rights-grabbing competitions:
Dave Sanger Photography
Photographers Matt Lutton and M Scott Brauer - dvafoto