what, and crawl the entire web to find infrigement?
Or pay for someone else to do it - but then, how would you enforce it? The costs of hiring a lawyer to threaten to sue would be greater than the money made from selling the typeface.
It's just a filename. It can be anything.
.. but it'll still be the same file. With checksums and binary diffs, not a big problem. There's even a business opportunity there!