one ethical disadvantage of unstructured interviews could be that it is a struggle to maintain the privacy of an interviewee
this could be because unstructured = very conversational and informal, which could cause the participants to feel uncomfortable with disclosing personal information because they don't want to give out their sensitive information
this means that participants may not want to take part in unstructured interviews which reduces the sample size, therefore limiting the amount of data gathered from the target population which can represent the general population. this causes unstructured interviews to be less representative
however, in unstructured interviews, the researcher has an opportunity to form a rapport with the participant. this could encourage them to give more in-depth data to improve the validity of the study, enabling more in depth conclusions to be drawn (interpretivists prefer)