The disadvantages of using WhatsApp include security concerns, data usage limits, and the addiction or overuse of the application. Regarding security, there have been concerns over how much data is collected by WhatsApp and how this data may be used or shared, as well as how easily conversations can be spread or even infiltrated. In terms of data usage, users may exceed their data limits if they are not careful, leading to extra costs related to data overages. Additionally, there is a concern that users may become addicted or overly dependent on WhatsApp for communication, which could lead to an unhealthy bias against using other forms of communication.