Any photo taken, no matter where it's found on the web, is the property of the photographer, unless the photographer has already released their rights. You cannot know, by viewing a photo, if the rights have been released. SO, if you see a photo on the web, and you DID NOT take that photo, you DO NOT have permission to use that photo, in any way, without getting PRIOR permission from the photographer.
ALL photos are the intellectual property of the photographer, the second the shutter is pressed. Posting that photo on the web does not change the "ownership" of that intellectual property in any way. Photos do NOT have to be watermarked, registered or have a copyright symbol or notice. Registering a photo does give the photographer MORE legal remedies, if the property is stolen.
So many people thinks is okay to Copy/Paste or Save As, any photo they see on the web. In reality, this is theft. Even the most "innocent" action of seeing an amazing photo on the web, thinking "that'd sure be pretty as my desktop," using Save As, and turning it into your desktop photo, IS theft of intellectual property. If that photo has been registered, the theft can result in even more "punishment" but a lack of being registered does not stop the photographer from coming after you nor does it mean a law has not been broken.
What if you notice one of the sponsors are using photo's that aren't theirs to sell products?
If you see this happening, please report it to staff members. In your report, it'd be helpful if you can supply a link to the original use of the photo.