I am not a lawyer. Most lawyers would tell you to get a lawyer. Most lawyers would tell you to not ignore them. The post at [extortionletterinfo.com...] would have some of what you are looking for.
The brief answer is that if you are the hosting site or person on record that they can find, then you are going to get the letter. I don't know what jurisdiction they have in Canada. I see no Canadian office, but they could have representatio there.
Removing the image is not enough for them, they want to collect from you by threatening you. So they troll sites, they unlawfuly steal your bandwidth in doing so and then they send a threatening letter. That is why you should block them in every way possible. You should inform all of the people on your site that they MUST license their images or take the pictures themselves.
At this time, Getty is going after only Rights Managed images because they have limited use rights and they cost $$$$$$$. The $1.00 - $5.00 images are not being targeted at this time. IF Getty could find traction with their claims, then they would go after everything, but there are not too many copyrights on $5.00 images, so they go after the more expenseive ones. They found in the USA, that if you don't have a copyright, you canot recover your legal costs and court cases for bulk filings of many images don't cary much of a penalty either, so Getty is not gettng traction on those.
BUT - Before you get a letter, stop it from happening in the first place. BLOCK their IP addresses, block sites that violates your Robots.txt file rules. Set a honeypot by having Robots.txt point to a fake and empty directory and then hide a link on the main page that point to it (use a small background color image or text with the background font) to point to that fake folder. Their bots will follow it and then you can ban them.
The following IP Addresses are the ones that we have blocked so far:
There are other BOTS that we block, but this is a good start. There are other bad bots out there. If bots ignore your Robots.txt file, then block them from coming back in the future. Plent of PHO and Perl script to automate the task if you are so inclined. I would like to see the virus and intrusion software companies step-it-up and kill these things off automatically at the server level with pre-page filtering.
Telling everyone that you know to get legal is a great ideas, but some may react too late. It is just not worth the hassle of dealing with Getty. If you host someone that has several Rights Managed Images, then the likelihood of Getty going to court would be higher since there is more $$$$$ for them to extort.
Can you look at an image and tell if it is rights managed? NO. Does Getty watermark images, not necessarily. Could the image have come from someone doing a search on the image and then they copied it? Absolutely! But not everyone knows about the law and when you get hit, it can be very expensive. Maybe the high school kid that did the site did not know about the law? Maybe we all need to know more. Just demanding payment is a BAD approach. Educating people about this is a far wider reaching approach. Bannin them at the server is just a safer bet in all cases. Their bots do not play by the rules, BAN THEM!