A company I worked for tried to remove a feature: One release added a "tagging" feature (similar to Gmail tags) while the next release had a "hierarchical fold

A company I worked for tried to remove a feature: One release added a "tagging" feature (similar to Gmail tags) while the next release had a "hierarchical folders" feature (similar to Outlook folders). The thinking was that tags and folders did pretty much the same thing, and folders were clearly superior since they were hierarchical. So we stripped the tagging and shipped with just the folder feature. Perhaps unsurprisingly, there turned out to be customers that had built a whole lot of import/export/processing infrastructure around the tags, and were less than happy about having to reimplement it all using folders. Plus they had a ton of tagged data and we hadn't included a tool to convert the old format to the new one. (Because we thought noone were using the tagging feature, it had only been in the product for a single release.) The lesson learned is that released features are similar to published APIs: If you remove or change them you will inevitably break something for someone.