UI is a subset of UX. Craigslist has a shitty UX, but it's free. The search is terrible, it's spammy, it's not semantic in any way, and post administration is

UI is a subset of UX. Craigslist has a shitty UX, but it's free. The search is terrible, it's spammy, it's not semantic in any way, and post administration is weak. But it's free. You could argue that being free is part of the UX, but I think that's a specious argument.