The World Wide Web is the wild wild west for intellectual property. Those esoteric concepts of copyrights and trademarks and patents often fall by the wayside for businesses looking to promote their business, or maybe even get their start, both online, and in the real world. Photos, videos, and other content are easily steal-able online, and just because it's easy, that doesn't make it legal. As such, businesses do need to be careful when selecting which photos and what type of media they want to use for promotional purposes.
If you're building your own website, or your web designer is asking you for photos, you can't just go and download any photo you see online. Even if you want to use a photo posted to Facebook, Twitter, or Yelp, on your website, you could face legal liability if you do not get permission from the photographer or from the website the photo is posted to. Luckily, social media makes it rather easy to contact users via in-site messaging.