Identifiable data such as name, telephone number and email address are often protected and removed. However, indirect identification could happen from the combination of non-identify data (such as Age, Ethnicity, Job titles, City) which could lead others to identify the participants.
People would probably identify me from job related identifications because there are only a few people doing the same role. For example, if there is a survey conducted in my organization, people will know that the data below belongs to me.

Province: ChiangMai
Job titles: Pharmacist, part time
Organization: Chain Drugstore