Developers take note: if you've got a mashup built off of Craigslist's data, don't even think about showing it to anyone who works there. At least, that's the lesson learned by developer Romy Maxwell, who says that Craigslist has blocked both his mashup and every single project built on Yahoo Pipes a few days after a friendly Email exchange he had with Craigslist founder Craig Newmark . Maxwell is one of the developers behind a new mashup called Flippity , which lets you plot Craigslist listings on a map. In a blog post, Maxwell writes that he had been having an Email exchange with Newmark over the last few weeks, during which Maxwell asked if the techniques employed by his project would be acceptable under Craigslist's restrictive Terms of Use. Newmark replied that " as a rule of thumb, [it's] okay to use RSS feeds for noncommercial purposes. " Since the project used RSS feeds and was non-commercial, that seemed to indicate that the project would be OK.