My understanding is that it happens enough that lawyers worry enough about it and therefore chase these things down constantly. Over the years I have received

My understanding is that it happens enough that lawyers worry enough about it and therefore chase these things down constantly. Over the years I have received cease-and desists from nice lawyers for Virgin Atlantic, The Coke-Cola Company (I had a Chrome extension called "Facebook Classic" that restored the reverse-chronological feed when FB started moving away from that), and an unofficial polite pre-lawyer request from The New York Times.