A couple of months ago I received a sternly worded email from a large online photo broker, informing me that one of the photos that I had in use on my website was a copyrighted photo, and that they would be following up to collect on that. Of course I immediately removed the photo, and searched the internet to see if others had received similar letters. It turns out that many people and companies receive these same notes -- some pay and some fight/negotiate to try and get the price down (in my case, the photo in question was listed on their website at about $1,100 - one thousand one hundred dollars - which seemed a little excessive, given that similar photos were available online for about $25.00).
The premise to fighting the offered fine is that you should pay no more than "market price" for the photo and that they will have to pay their in-house attorneys to also negotiate on their end, and that eventually you'll wear them down.
Their offer for the photo, in a subsequent email, was $250 for the photo, and that I would also get a small discount on their annual subscription service for unlimited use of their photos. So now the "fine" had become a thinly disguised marketing outreach for a service that was priced well above similiar online services. I politely declined their offer but did pay their fine -- both to get it out of my in-box and to acknowledge that I had unknowingly used their photo without their permission.
Lesson learned -- and of course they are in business to make money. Likewise, their freelance photographers have to get paid for their expertise, the hours they spend upgrading their skills, and the constant upgrades to equipment and software -- none of which is inexpensive.
So of course I've since been through my website with a fine-tooth comb to make sure that I don't have any copyrighted photos in use, and I'm shopping for a photo subscription service that is priced a little more in line with my budget. Note that if your website or blog is a not-for-profit site, they are much more lenient with regard to the use of copyrighted photos (they generally just want you to give photo credit to their company / their photographer -- which is more than fair).