Right. Now are beginning to make a little sense -- a big change from the OP. So, the problem was not getting the data from Craigslist but publishing it elsewh

Right. Now are beginning to make a little sense -- a big change from the OP. So, the problem was not getting the data from Craigslist but publishing it elsewhere. But your point still will not make Craigslist at all happy: Craigslist has a lot of data. Maybe someone, Tom, wants to get a copy of a lot of that data and do some things with it. The data at issue need not be in any meaningful way subject to the marking you describe. That is, what Craigslist sends is HTTP, HTML, CSS, simple text, and maybe some files in JPG, PNG, GIF, etc. Tom can grab just the text, put it into a database, analyze it, and republish leaving the marking far behind. So, right, if Tom does something sufficiently stupid, then he can be slapped down for violating the C&D letter. Otherwise, not stupid, it's essentially impossible for the Web site to know if Tom honored the C&D letter. Then, searching Tom's computer, etc. will be based on next to no go evidence and be wildly unfair to Tom.