[andrewingram]

Not even just user-defined fields, any time where the fields need to be defined as data values rather than part of your concrete data model. Product attributes on a big multi-category e-commerce site being another example. You could just stick them in JSON, but it's still essentially EAV, just with a different storage mechanism.

Another advantage of EAV as a pattern, is it makes it straightforward to add metadata to values, like "where did this value come from?". For systems with audit trails, just having keys and values isn't enough.

EAV wouldn't be the first tool I'd jump to -- I've definitely seen it go wrong -- but it feels like it's going too far to call it an anti-pattern.