APIs introduce a more long-term maintenance burden than GUIs. If you take away a checkbox that hardly anyone used, no big deal, a few people are momentarily co

APIs introduce a more long-term maintenance burden than GUIs. If you take away a checkbox that hardly anyone used, no big deal, a few people are momentarily confused. But if you take away an API call parameter that hardly anyone used, a few people still depended on it, and maybe the change broke their systems and caused them to lose business until they patched it. Then they complain online, cancel their agreements with you, scare away your potential customers... it can be a disaster. Everything you put in your API documentation is a promise. Facebook gets away with frequent, breaking API changes because they have a monopoly. Until you can say the same, it might be a good idea to keep your API stable.