The real issue was that HHV became a huge hit and was doing a lot, a lot of business. But as CT said, using the images was no bueno.
I'm guessing WB probably hires a couple college interns who do nothing but go around looking for naming violators. The kids are all enthusiastic so when they find some guy violating they can run up to their bosses and show them how they busted someone and receive all their kudos.
"Mr. Dithers, Mr. Dithers, look what I did!"