A WARNING FOR ALL WEBMASTERS!!
A client of mine has received a letter and invoice from Getty Images for unlawful use of images on his old website. We took over this website from a previous freelance designer 4 months ago and previous images from the old website were the cause EVEN THOUGH they no longer existed on the new site pages or server. Whether they sweeped the site a while back or took the data from www.archive.org we don't know.
The invoice was for over USD$1000 PER IMAGE and the total amounted to nearly USD$6000. Naturally, my client was panicked - the terms of the letter from Getty Images are very strongly worded and he nearly paid up until I did some investigating.
While I won't go into all the issues suffice to say if any other people are getting these letters and demands for payment from Getty for unlawful use of images please visit the following thread:
Unauthorised Use of Getty Images at www.sitepoint.com/forums/
Essentially, Getty Images are sweeping the net using PicScout bots to find any unauthorised use of images - fair enough - they have to protect their intellectual property.
Instead of complying with the DMCA and issuing a takedown order (cease and desist) they send an invoice to the domain owner demanding payment - even if the owner removes the images.
So - if you are unsure of the legal position of any images I would replace them with images from http://www.sxc.hu/ (I would say www.istockphoto.com but Getty own them now!). Even this may not protect you, as they may access historical data. You might want to exclude the archive.org bot from your site or images folder - see http://www.archive.org/about/exclude.php
More info on the Picscout bot
So far there is no evidence of Getty taking anyone to court over this - they seem to be bullying mom and pop and small business sites.