And do what Andrew says and you don't even have to sue most of hte time just a nice threatening letter (Note: NOT E-Mail but an official overnight air document to them telling them you WILL take legal action if they don't stop.. Best $22 to get someone to stop
By the way, that $45 applies to each image. Most photographers don't register their copyrights because of this, meaning they typically can't do anything more than send a c&d. I've seen some very unique abuses of this by big brained lawyers.