For some time now Getty (and Corbis) stock photo publishers have been using a standard, and presumably very profitable, approach towards websites which use images from their libraries without paying. They claim it matters not whether the infringer was aware they were using images which should have been licensed. They use a company based in Israel to find the infringing images, using image searching software, then they claim outlandish sums from the infringer, with the threat of a larger claim via legal action made. What happens next can take various paths, detailed here...

http://www.fsb.org.uk/discuss/forum_posts.asp?TID=1106

As stated on the forum, Getty may have tried to take only one company to court over this. The case was settled before reaching court...

http://www.out-law.com/page-10367

...so we still don't know how the courts would assess such a claim.