According to the NESH's Guidelines, research projects that include persons must generally only be initiated after securing the subjects' free and informed consent (point 9). In other words, researchers must weigh relevant considerations and determine whether it is necessary to obtain consent or not. This general rule also applies to research on/using the Internet.
There are many difficulties in connection with obtaining consent in digital forums. First, a request for consent to participant observation may be destructive for the very interaction the researcher wishes to study. Second, participation itself is ephemeral, while the information the researcher wants to use may be stored and available. As a result, contacting the people from whom consent is desired after the event may be difficult. Third, in some cases people pretend to be someone other than themselves. This means that a researcher cannot be sure that the consent has been obtained from the person from whom consent was desired.
In cases where consent is necessary, these practical problems make demands on planning the research. Obtaining consent over the Internet also requires greater efforts to guarantee the quality of the consent. This means that greater precautions must be taken to ensure that persons are not recruited who should not be participating in the study, for example children in studies targeted at adults. Another problematic issue may be to ensure that the subjects adequately and correctly understand the information provided concerning the research and why the researcher requests consent, if this information is communicated in writing only, and over the Internet. In some cases, problems obtaining consent may require that the researcher should refrain from studying the forum altogether.
There is a distinction between researchers merely mining data and actively participating in a forum. If they actively participate in a forum with access restriction, researchers should present their intentions. Such disclosure should take place before starting the research. Similarly, there may also be reasons to make oneself known if information is obtained without active participation in the forum. Researchers must nevertheless take due consideration of ethical norms and any rules regarding behaviour that may apply to the forum. Researchers are responsible for clearly explaining to research subjects their role and the expectations, limitations and requirements that pertain to their role as researcher (point 19).
The consideration of respect for the subjects calls for the researcher to also inform subjects in open forums about systematic registration (e.g. recording) or reporting of information when possible.