1. Root Privileges: Running `iotop` typically requires root privileges because it needs access to kernel-level I/O statistics. This means you need to run it with `sudo`, which might not always be feasible or desired for all users.

2. System Impact: Monitoring I/O usage in real-time can consume system resources itself, potentially affecting the overall system performance. This impact might be more pronounced on systems with heavy I/O loads or limited resources.

3. Limited Historical Data: `iotop` provides real-time data but does not offer a history of disk I/O usage over time. If you need to analyze historical I/O patterns or trends, you might need to complement `iotop` with other tools that collect and store historical data.

4. Complexity and Learning Curve: Understanding the various columns and data presented by `iotop` might require some familiarity with disk I/O concepts and Linux internals. This can be a challenge for users who are not well-versed in these areas.

5. Dependency and Availability: `iotop` might not be installed by default on all Linux distributions. Users need to ensure that it is available on their system or install it using package managers.

6. Non-Standard Behavior: Different versions of `iotop` might have slightly different behavior and options depending on the distribution and version of Linux. This can lead to inconsistencies when moving between different systems.

7. Process Identifier (PID) Changes: In systems with dynamic processes, the PIDs of processes can change over time. This can make it challenging to track specific processes’ I/O usage accurately.

8. External Dependencies: `iotop` relies on the `python` and `psutil` libraries to gather and display I/O information. If these dependencies are not present or configured correctly, `iotop` might not function as expected.

Despite these potential problems, `iotop` remains a valuable tool for gaining insights into real-time disk I/O usage by processes on a Linux system. Users can manage and mitigate these issues by considering the limitations and being aware of the potential impact on their system’s performance.